Ringworm in Dogs: What It Looks Like, and Costs
Ringworm is a fungal infection of the hair and the surface of the skin, and the name is the first thing that misleads. This needs a same-day appointment if any of these are true: A rapidly spreading bald or crusted area, or a raw painful patch; A nodule or lump on the muzzle or a leg that has appeared over days.
Is this an emergency?
Worst first. Find the highest rung that matches what you can actually see, and act on that one — not on the one you hope applies.
- Same dayGet an appointment today. If your own practice is full, an urgent-care clinic counts.
- A rapidly spreading bald or crusted area, or a raw painful patch
- A nodule or lump on the muzzle or a leg that has appeared over days
- Skin lesions in a puppy that is also unwell, not growing, or off its food
- Skin lesions in a dog living with a baby, an elderly person or someone on immune-suppressing treatment
- Any skin lesion where the household has developed itchy rings on the skin at the same time
The reason to be seen quickly is rarely the fungus itself - it is what else the lesion could be, and who else is exposed. Merck notes that in a puppy with multifocal hair loss, scaling and crusting, the two major differential diagnoses are dermatophytosis and demodicosis, which are treated completely differently. Merck also describes nodular lesions - kerions - developing in dogs, which look alarming and need distinguishing from a tumour or a deep bacterial infection. And Merck states the disease is zoonotic, so a household where people have developed lesions too should not be waiting for an appointment next month.
- Routine — book an appointmentBook in the next few days and keep an eye out for anything on a rung above.
- One or more patches of hair loss with scaling or crusting, in a well dog
- A circular or irregular bald patch that is slowly enlarging
- Broken, stubbly hair over a patch of grey or reddened skin
- Darkened or thickened skin in a patch, with or without itching
- Brittle, deformed or crumbling claws with inflammation at the nail bed
This is where the diagnosis gets made, and it needs a test rather than a look. Merck is explicit that no single test is a gold standard - typically several are used together - and the reason is that nothing about the appearance is specific. Merck's own sign list is any combination of hair loss, scaling, crusting, erythema, papules, hyperpigmentation and variable itch, which describes most of dermatology. Do not start an over-the-counter antifungal cream first: it can make hairs harder to find and cultures harder to read.
- Monitor at homeNo visit needed yet. Watch for anything on a rung above and re-read this page if it appears.
- A dog under treatment with lesions that are resolving
- A healthy in-contact dog or cat in a household where one animal is infected
- A young, free-roaming or hunting dog with no lesions
Merck lists young age, free-roaming or hunting activity and warm environments as risk factors in dogs, and notes disease is more common in animals under physiological stress or in overcrowded settings such as hoarding situations. For the dog under treatment, the endpoint is not what the skin looks like: Merck says the end of treatment requires both clinical cure - all lesions resolved and no new ones - and mycological cure, confirmed by a negative fungal culture or PCR.
Key facts
- When it is an emergency
- This condition has no emergency rung on our record — see the data note below for why, and the top rung of the ladder for what does need attention today.
- Affects
- Dogs
- Also known as
- what does ringworm in a dog look like, dermatophytosis, fungal skin infection in dogs, Microsporum canis in dogs, dog fungus
- Cost range on this page
- $56–$1,110 — from routine vet checkup (wellness exam) to dog biopsy
- Biggest single bill
- Dog Biopsy, $144–$1,110, $465 typical
- Covered by pet insurance
- Usually, under an accident-and-illness policy taken out before the signs started. 70-90% of the covered bill after the deductible, where the sign being investigated first appeared after the waiting period ended.
- Outlook
- Merck: dermatophytosis is a self-limiting disease that resolves without treatment in otherwise healthy animals, and resolution of infection takes 6 to 12 weeks.
- Clinical facts last verified
- 2026-08-29
The name is the first thing that misleads. Merck's description of what dermatophytosis actually looks like in dogs is any combination of hair loss, scaling, crusting, redness, small bumps, darkened skin and variable itch — which describes most of dermatology, and does not describe a ring.
The Wood's lamp claim that gets dogs misdiagnosed
The widely repeated figure is that only about half of Microsporum canis strains fluoresce. Merck cites an evidence-based review finding that 91 to 100% of untreated, infected animals will have glowing hairs.
That difference is not academic. A negative lamp exam gets used to rule the disease out, and if the true rate is above 90% then the technique, not the fungus, is usually what failed. Merck's technique is specific: a plug-in lamp with built-in magnification, held within 2 to 4 cm of the skin, in a darkened room the examiner's eyes have adapted to, moving slowly from the head.
Only hair shafts glow apple green — not crusts — so crusts are lifted to look underneath. And fluorescence becomes less common as an animal recovers, so the figure applies to untreated animals.
Is this actually a common disease?
Less common than the internet suggests. Merck puts true disease prevalence at under 4% of all skin disorders and states directly that it is not the most common skin disease of cats, contrary to what is reported in lay literature.
That figure needs reading carefully, and we are not carrying it into the prevalence field for this record. It is a share of a caseload of skin disease, not a proportion of a defined population of dogs. It tells you what proportion of itchy, scaly patients turn out to have ringworm; it does not tell you your dog's risk.
The commoner explanations for the same appearance are bacterial pyoderma and Malassezia overgrowth, and in a puppy with multifocal hair loss, scaling and crusting Merck names demodicosis as the other major differential — treated completely differently.
Why this record has no emergency rung
Because Merck describes dermatophytosis as a self-limiting disease that resolves without treatment in otherwise healthy animals. The fungus itself is not going to kill a dog, and we are not going to manufacture an urgency to fill a slot.
The same-day rung above exists for two other reasons. The first is what else a spreading or nodular lesion can be — Merck describes kerions, nodular lesions that look alarming and need distinguishing from a tumour or a deep bacterial infection. The second is the household: this is a zoonotic disease, and a home with a baby, an elderly person or someone on immune-suppressing treatment should not be waiting for an appointment next month.
Do not put cream on it before the appointment
An over-the-counter antifungal makes infected hairs harder to find and cultures harder to read, and the diagnosis here needs a test rather than a look. Merck is explicit that no single test is a gold standard — typically several are used together.
Direct microscopy is the cheap, same-visit one: Merck reports that hair and scales plucked from lesions and mounted in mineral oil confirm infection in more than 85% of cases, with infected hairs appearing wide and pale against normal thin threadlike ones.
Culture has its own preparation rule that people get wrong: Merck warns hair should not be wiped with alcohol first, because that can produce a false negative. Sample the lesions, not the whole coat, using a new unopened toothbrush.
When does treatment actually stop?
Not when the coat looks normal. Merck's endpoint is both clinical cure — all lesions resolved and no new ones — and mycological cure, confirmed by a negative fungal culture or PCR, which it puts at four to six weeks or more.
Stopping on appearance is one of the two things Merck names as turning a straightforward case into a long one. The other is treating a single animal in a household where several are infected.
Topical therapy is required in addition to systemic treatment rather than instead of it, because the infective spores sitting on the coat are the source of contagion — and Merck says topical treatment continues to mycological cure even if the tablets have stopped.
The environment is easier to fix than you have been told
Merck corrects a genuine misconception here: spores do not multiply in the environment and do not invade it like mildew. They are a dormant life stage and are easily removed.
So mechanical removal comes first — vacuuming and wiping away hair and organic material, then washing surfaces with detergent until visibly clean. Disinfectant goes on afterwards, and disinfectant alone will not do it. Bedding and towels are handled by thorough machine washing, and Merck notes bleach is not needed. Thorough cleaning once or twice a week is adequate.
The transmission route worth changing is the groomer's. Merck states that transmission from environmental spores is inefficient unless there is microtrauma to the skin — for example clipping the coat with contaminated clippers — so use a groomer that disinfects equipment between dogs.
Which fungus, and why it is often on the nose
Merck names three pathogens of veterinary importance. Microsporum canis affects cats, dogs and, to a lesser extent, large animals. Trichophyton mentagrophytes is the second. Nannizzia gypsea — formerly Microsporum gypseum — is a soil organism that causes inflammatory lesions.
The soil one explains the presentations that look nothing like the pictures. Merck's own illustrative case is a dog with nodular lesions on the muzzle and nose from rooting around in dirt: a face-first infection in a terrier-shaped dog, with no ring anywhere on it.
Merck also notes that mere exposure does not always result in disease, and that severity reflects the host rather than the strain — severe infections are not caused by more virulent organisms but by a failure of host cell-mediated immunity to respond. That is why the badly affected animals are the ill, the stressed, the very young and the ones with something else going on, and why Merck lists young age, free-roaming or hunting activity, warm environments and overcrowded settings such as hoarding situations among the risk factors in dogs.
Which drugs work, and which are named as failures
Merck is unusually specific about what not to use. Fluconazole is named as the least effective drug against dermatophytes. Griseofulvin is superseded, because itraconazole and terbinafine are superior with lower risk. And lufenuron is simply ineffective.
That list matters because all three still circulate as recommendations. So does one piece of household advice Merck contradicts: isolation is correct, with a limit — infected young animals should not be confined for long periods or under-socialised, or lifelong behavioural problems may result. Both halves of that sentence belong in a puppy's plan.
The drug choice itself is a prescription decision made on the dog's weight and liver function, and Merck's framing of the whole treatment is worth keeping in view: infections in otherwise healthy animals are self-limiting and do not require treatment, but animals are treated anyway to shorten the course and to minimise contagion to other animals and to people.
What it costs, and the part we cannot price
This is the shortest cost join in our dataset, and that is a disclosure rather than an oversight.
The diagnostic consultation is $56–$130 nationally with $66 typical, and it covers the examination, the lamp, the direct microscopy and the decision about which animals in the household need testing. A biopsy at $144–$1,110, typical $465, is not needed for a routine case — Merck reserves it for nodular lesions and unusual presentations, with the instruction to tell the laboratory dermatophytosis is on the differential list so special stains are used.
What we cannot price is where the money actually goes: four to six weeks or more of oral antifungal medication sized to the dog, plus twice-weekly whole-body rinses, plus a repeat culture to confirm cure. Merck notes small dogs can be treated cost-effectively with itraconazole while larger dogs may be cheaper on ketoconazole or terbinafine, so the drug bill scales with body weight in a way the consultation does not. Until we publish a record for recurring dermatology medication, the figures in the section below are the visit and the biopsy, and they should not be read as the cost of the treatment.
Why ringworm in dogs (dermatophytosis) happens
- Microsporum canis and the other dermatophytes
- Merck names the pathogens of veterinary importance: Microsporum canis, which affects cats, dogs and to a lesser extent large animals; Trichophyton mentagrophytes; and Nannizzia gypsea, formerly Microsporum gypseum, a soil organism that causes inflammatory lesions. The genera Microsporum and Trichophyton have been reclassified into Arthroderma.
- Direct contact with an infected animal
- Merck: transmission is by direct contact with an infected animal, but mere exposure does not always result in disease. This is why one dog in a household can be infected and another, in the same house, never is.
- Microtrauma to the skin
- The mechanism most owners have never heard and the one that explains grooming outbreaks. Merck: transmission from spores in the environment is inefficient unless there is microtrauma to the skin - for example clipping the coat with contaminated clippers. Lesion development requires enough spores, microtrauma, and moisture, and under ideal conditions arthrospores can germinate and start invading skin and hair shafts within 6 to 8 hours.
- Digging and rooting in soil
- Nannizzia gypsea lives in soil, and Merck's own illustrative case is a dog with nodular lesions on the muzzle and nose from rooting around in dirt. This is a face-first infection in a terrier-shaped dog and it looks nothing like a ring.
- The dog's own immune response
- Merck: the severity of infection reflects the host's overall health, and severe infections are not caused by more virulent strains but by a failure of host cell-mediated immunity to respond. That is why the badly affected dogs are usually the ill, the stressed, the very young and the ones with something else going on.
How a vet diagnoses ringworm in dogs (dermatophytosis)
Not every test below is run on every animal. Which ones are depends on what the examination finds, and each one is priced in the cost section further down.
- Physical and dermatological examination
- Establishes the distribution and rules in the differentials - Merck names demodicosis as the other major diagnosis in a puppy with multifocal hair loss, scaling and crusting, and pustular disease can mimic dermatophytosis. The exam is also when the in-contact animals get looked at. What it costs
- Wood's lamp examination
- Worth stating precisely, because the myth in circulation is that only about half of Microsporum canis strains fluoresce. Merck cites an evidence-based review finding that 91-100% of untreated, infected animals will have glowing hairs. The technique matters: a plug-in lamp with built-in magnification, held within 2 to 4 cm of the skin, in a darkened room the user's eyes have adapted to, moving slowly from the head; only hair shafts glow apple green, not crusts, so crusts are lifted to look underneath. Fluorescence becomes less common as an animal recovers.
- Direct microscopic examination of hair and scale
- Merck: hair and scales plucked and scraped from lesions and mounted in mineral oil can confirm infection in more than 85% of cases, and no clearing agent is needed. Infected hairs appear wide and pale against normal hairs that are thin and threadlike, with cuffs of spores on the outside of the shaft. This is a same-visit test with no laboratory fee.
- Fungal culture
- Merck: sample only the lesions, not the whole coat, using a new unopened toothbrush brushed over the lesions and then inoculated onto dermatophyte test medium. Plates are incubated at room temperature, sealed in a bag, and examined daily for 14 days; pathogens are pale, never heavily pigmented. Merck warns that hair should not be wiped with alcohol first, because that can produce a false negative.
- PCR assay
- Merck: confirms the presence or absence of fungal DNA on the coat, but cannot distinguish viable from non-viable spores, and needs more than 20 hairs and crusts submitted. Useful for confirming cure, with the caveat that dead spores still test positive.
- Skin biopsy
- Merck: not indicated in routine cases, but indicated where there are nodular lesions or an unusual presentation. Merck's practical instruction is to tell the laboratory that dermatophytosis is on the differential list so special stains are used, and to submit several 8 mm punch samples or the whole nodule. What it costs
How ringworm in dogs (dermatophytosis) is treated
- Diagnosis and a treatment plan
- The visit that decides whether this is ringworm, demodex, a bacterial pyoderma or an allergy, and which of the household's animals need treating. Merck's framing is that infections in otherwise healthy animals are self-limiting and do not require treatment, but that animals are treated anyway to shorten the course and minimise contagion to other animals and to people. What diagnosis and a treatment plan costs
- Systemic antifungal medication
- Merck: small dogs can be treated cost-effectively with itraconazole, and larger dogs with ketoconazole or terbinafine, which may be more cost-effective at size. Treatment continues until mycological cure - a negative culture or PCR - which Merck says can take four to six weeks or more. Merck also names what not to use: fluconazole, because it is the least effective drug against dermatophytes; griseofulvin, because itraconazole and terbinafine are superior with lower risk; and lufenuron, which is simply ineffective. Doses are prescription decisions made on the dog's weight and liver function.
- Topical therapy to disinfect the coat
- Merck is emphatic that this is required in addition to systemic treatment, not instead of it, because the infective spores on the coat are the source of contagion. A whole-body rinse of lime sulfur at 1:16 or enilconazole at 1:100 twice weekly has residual activity; a 2% chlorhexidine with 2% miconazole shampoo is effective but has no residual activity and must be used two to three times a week. Merck says topical therapy continues until mycological cure even if the tablets have stopped.
- Environmental cleaning
- Merck corrects a common misconception here: spores do not multiply in the environment and do not invade it like mildew - they are a dormant life stage and are easily removed. Mechanical removal of hair and organic material by vacuuming or wiping, then washing surfaces with detergent until visibly clean, is the most important step; disinfectant afterwards, but disinfectant alone will not do it. Bedding and towels are disinfected by thorough machine washing and Merck notes bleach is not needed. Thorough cleaning once or twice a week is adequate.
- Isolation, with a limit
- Merck: infected animals should be kept away from other pets until there is clear evidence of clinical cure - but adds a caveat that matters for a puppy, which is that infected young animals should not be confined for long periods or under-socialised, or lifelong behavioural problems may result. Both halves of that sentence belong in the plan.
- Biopsy where the lesion is not behaving
- For nodules, for lesions that do not respond, and for anything that does not fit - to exclude the tumours and deep infections that a kerion can imitate. What biopsy where the lesion is not behaving costs
Outlook and prevention
Merck: dermatophytosis is a self-limiting disease that resolves without treatment in otherwise healthy animals, and resolution of infection takes 6 to 12 weeks. Treated, dogs are treated until mycological cure, which Merck puts at four to six weeks or more. Animals that are ill, stressed or have another underlying disease are harder to treat, partly because medicating them is harder and partly because they may not mount the cell-mediated immune response recovery depends on. In people, Merck notes the disease causes skin lesions that are easily treated. The two things that turn a straightforward case into a long one are stopping treatment on appearance rather than on a negative test, and treating one animal in a household where several are infected.
Most of the practical prevention is grooming and household hygiene rather than avoidance. Merck's transmission mechanism points straight at it: contaminated clippers and the microtrauma they cause are an efficient route, so use a groomer that disinfects equipment between dogs. Isolate and test new arrivals, particularly kittens and puppies from shelters, hoarding situations or crowded breeding environments, which Merck names as higher-risk settings. Wash hands after handling a dog with any skin lesion, and take the household seriously - Merck classes this as a zoonotic disease. If a dog is diagnosed, clean mechanically first and use a bathroom disinfectant labelled effective against Trichophyton, and keep going until mycological cure rather than until the coat looks normal.
What treating ringworm in dogs (dermatophytosis) costs
Costs for ringworm in dogs (dermatophytosis) run from $56 for routine vet checkup (wellness exam) to $1,110 for dog biopsy. A severe case can run past the top of that range — what treatment adds depends on how bad it gets.
Each block below is one procedure we price in full: the national range, the region-by-region table behind it, and how every row was sourced. Rows marked published come from a real price for that geography; rows marked indexed are the national range scaled by a cited regional cost index, and we label them rather than blending the two.
Routine Vet Checkup (Wellness Exam)
$56–$130Routine Vet Checkup (Wellness Exam) costs $56 to $130 in the United States, and $66 is the typical price.
| Region (basis) | Low | Typical | High |
|---|---|---|---|
| Northeast (published) | $64 | $76 | $101 |
| Midwest (published) | $58 | $63 | $67 |
| South (published) | $57 | $63 | $98 |
| West (published) | $63 | $72 | $129 |
| Hawaii (most expensive jurisdiction) (published) | $127 | $128 | $129 |
| Mississippi and West Virginia (least expensive jurisdictions) (published) | $57 | $57 | $58 |
| Published private-practice fee schedules, 8 clinics in 8 states (published) | $65 | $78 | $92 |
published — a real price for that geography was found and cited. indexed — the national range scaled by a cited regional cost index, because no geography-specific price is published. All 7 rows are published prices. Prices last verified 2026-08-28. Full sourcing in Sources.
How each regional row was sourced
- Northeast (published)
- Published state averages in the Northeast run from Pennsylvania $64 (dog) and $66 (cat) to Massachusetts $99 and $101, median $76 for dogs against a $66 national median (CareCredit/ASQ360 2025-2026 50-state survey).
- Midwest (published)
- Published state averages in the Midwest run from Kansas $58 (dog) and $60 (cat) to Wisconsin $66 and $67, median $63 for dogs. This is the tightest region in the country - only $9 separates its cheapest state from its most expensive (CareCredit/ASQ360 2025-2026).
- South (published)
- Published state averages in the South run from Mississippi and West Virginia at $57 (dog) and $58 (cat) to the District of Columbia at $97 and $98, median $63 for dogs. The region contains both the cheapest jurisdictions in the country and the second most expensive (CareCredit/ASQ360 2025-2026).
- West (published)
- Published state averages in the West run from New Mexico $63 (dog) and $65 (cat) to Hawaii $127 and $129, median $72 for dogs (CareCredit/ASQ360 2025-2026).
- Hawaii (most expensive jurisdiction) (published)
- $127 for a dog and $129 for a cat, the highest of all 51 US jurisdictions in the 2025-2026 CareCredit/ASQ360 survey - 2.2 times the Mississippi and West Virginia figure for the identical examination.
- Mississippi and West Virginia (least expensive jurisdictions) (published)
- Both states publish at $57 for a dog and $58 for a cat, the joint lowest of all 51 US jurisdictions in the 2025-2026 CareCredit/ASQ360 survey.
- Published private-practice fee schedules, 8 clinics in 8 states (published)
- Actual posted exam fees, not survey averages: Rocket City Mobile Vet, Huntsville AL $65; Tequesta Veterinary Clinic, FL $69 ($74 for a new patient); Cane Bay Veterinary Clinic, Summerville SC $74; Midvalley Animal Clinic, Taylorsville UT $75; Love City Vet, Philadelphia PA $78; Modern Animal $85 pay-as-you-go; Dallas Veterinary Clinic, TX $90; Covina Animal Hospital, CA $90; Kenmore Veterinary Hospital, WA $92. Every one of these sits above its own state's survey median.
The itemized invoice, the drivers behind the spread and the full sourcing are on our routine vet checkup (wellness exam) cost breakdown.
Dog Biopsy
$144–$1,110Dog Biopsy costs $144 to $1,110 in the United States, and $465 is the typical price.
| Region (basis) | Low | Typical | High |
|---|---|---|---|
| Northeast (indexed) | $156 | $502 | $1,199 |
| Midwest (indexed) | $127 | $409 | $977 |
| South (indexed) | $128 | $414 | $988 |
| West (indexed) | $145 | $470 | $1,121 |
| Clayton, North Carolina (published) | $144 | $465 | $1,110 |
published — a real price for that geography was found and cited. indexed — the national range scaled by a cited regional cost index, because no geography-specific price is published. 1 of 5 rows are published prices; 4 are indexed. Prices last verified 2026-08-28. Full sourcing in Sources.
How each regional row was sourced
- Northeast (indexed)
- No published price specific to this region was found for this procedure. The national range is shifted by the 7.5% above national regional cost ratio measured from the CareCredit/ASQ360 2025-2026 50-state price tables, where the region-to-national ratio held to within half a percent across every procedure surveyed. Treat as an estimate.
- Midwest (indexed)
- No published price specific to this region was found for this procedure. The national range is shifted by the 11.6% below national regional cost ratio measured from the CareCredit/ASQ360 2025-2026 50-state price tables, where the region-to-national ratio held to within half a percent across every procedure surveyed. Treat as an estimate.
- South (indexed)
- No published price specific to this region was found for this procedure. The national range is shifted by the 11.3% below national regional cost ratio measured from the CareCredit/ASQ360 2025-2026 50-state price tables, where the region-to-national ratio held to within half a percent across every procedure surveyed. Treat as an estimate.
- West (indexed)
- No published price specific to this region was found for this procedure. The national range is shifted by the 1.5% above national regional cost ratio measured from the CareCredit/ASQ360 2025-2026 50-state price tables, where the region-to-national ratio held to within half a percent across every procedure surveyed. Treat as an estimate.
- Clayton, North Carolina (published)
- Veterinary Medical Center of Clayton publishes biopsies from $144, bloodwork from $90 and growth removal at $175-$875 with anaesthesia or sedation included. The national range on this page is built from those three published lines, so this row is the national range rather than a variation on it.
The itemized invoice, the drivers behind the spread and the full sourcing are on our dog biopsy cost breakdown.
What the invoice for dog biopsy looks like
Dog Biopsy is the largest single bill on this page, so this is the one worth reading line by line. Clinics quote a bundled number and itemize afterwards; this is the decomposition.
| Line item | Low | High |
|---|---|---|
| Examination CareCredit national average for a routine vet visit for a dog | $56 | $129 |
| Fine needle aspirate and cytology, laboratory fee Iowa State $43.00 for cytologic interpretation per organ system; University of Missouri $48.50, or $72.00 for multiple lymph nodes | $43 | $72 |
| Pre-anaesthetic bloodwork Veterinary Medical Center of Clayton publishes bloodwork from $90; CareCredit's national averages are $104 for a CBC and $164 for a chemistry panel | $90 | $268 |
| Surgical biopsy with sedation or anaesthesia Veterinary Medical Center of Clayton publishes growth removal at $175-$875, with anaesthesia or sedation already included in the price | $175 | $875 |
| Histopathology, laboratory fee Ohio Department of Agriculture $55.00 for a second-opinion read, $60.00 for a routine biopsy, $90.00 over 5 cm; University of Missouri $90.00; Iowa State $100.00 to $165.00 by size | $55 | $165 |
| Histopathology as billed to you Veterinary Medical Center of Clayton publishes biopsies from $144, against the $55-$165 the laboratory charges the practice. The '+' in 'from $144' is doing real work here | $144 | $144 |
| Each additional mass submitted Iowa State $30.00 each; Ohio Department of Agriculture $54.00 as a mass add-on | $30 | $54 |
| Immunohistochemical staining Iowa State $35.00; University of Missouri $43.00 | $35 | $43 |
| Decalcification for a bone sample Iowa State | $30 | $30 |
| Ultrasound-guided or CT-guided sampling CareCredit national averages: $483 for an ultrasound, $1,615 for a CT scan. This is the imaging, not the sampling | $483 | $1,615 |
Not every line appears on every invoice — practices bundle differently, and some of these are only billed when the procedure turns up something. Sourcing for each figure is in Sources.
Does pet insurance cover ringworm in dogs (dermatophytosis)?
Dog Biopsy is normally covered by a standard accident-and-illness policy. A biopsy taken to investigate a new problem is covered by an accident-and-illness policy; a biopsy taken as part of routine screening is not. The pre-existing rule bites in an unusual way here, because the biopsy is often the moment a condition is formally diagnosed - if the lump or the sign was already in the record before enrolment, the biopsy that names it is still investigating a pre-existing condition.
What you would get back: 70-90% of the covered bill after the deductible, where the sign being investigated first appeared after the waiting period ended.
The catch, and it is the one that matters here: every US carrier excludes pre-existing conditions. If your animal has already been seen for ringworm in dogs (dermatophytosis) — or for signs a vet later links to it — a policy bought today will not pay for this episode. Cover is something you buy before the diagnosis, which is why the $56–$1,110 above is worth knowing while your pet is still well.
Waiting periods, and what each carrier counts as pre-existing, differ enough that the only useful answer is a side-by-side: our pet insurance comparison for dog biopsy shows which policies pay for it, how long the wait is, and how each one words the pre-existing exclusion.
Common questions
Is ringworm in dogs (dermatophytosis) an emergency?
Our record carries no emergency rung for this condition. This record has no emergency rung, and that is a deliberate clinical statement rather than an omission. Ringworm in a dog is not a same-night emergency: Merck describes it as a self-limiting disease that resolves without treatment in otherwise healthy animals. The signs on the same-day rung are there because of what else a spreading or nodular skin lesion can be, and because the disease is zoonotic in a household that may include immunocompromised people, not because the fungus itself is dangerous to the dog. No prevalence field is filled in. Merck's figure - true disease prevalence reported at under 4% of all skin disorders - is a share of a caseload of skin disease, not a proportion of a defined population of dogs, so it has no denominator that would make it a prevalence in the sense this dataset uses the word, and it is quoted in the summary with that framing instead. The Wood's lamp figure of 91-100% is Merck's citation of an evidence-based review and it directly contradicts the widely repeated claim that only about half of Microsporum canis strains fluoresce; it is quoted because the older claim causes real harm, in that a negative lamp exam is used to rule the disease out when the technique was the problem. The World Association for Veterinary Dermatology consensus guidelines are cited as the underlying source that Merck's entry draws on; the specific figures quoted above are taken from the Merck entry itself, which is the version we were able to read in full. The cost join is short - the consultation and a biopsy - because the real spend on this condition is weeks of oral antifungal medication plus twice-weekly whole-body rinses, and we do not publish a price record for either. The most urgent rung is "Same day": A rapidly spreading bald or crusted area, or a raw painful patch; A nodule or lump on the muzzle or a leg that has appeared over days; Skin lesions in a puppy that is also unwell, not growing, or off its food.
How much does it cost to treat ringworm in dogs (dermatophytosis)?
Costs for ringworm in dogs (dermatophytosis) run from $56 for routine vet checkup (wellness exam) to $1,110 for dog biopsy. A severe case can run past the top of that range — what treatment adds depends on how bad it gets.
How is ringworm in dogs (dermatophytosis) diagnosed?
Physical and dermatological examination: Establishes the distribution and rules in the differentials - Merck names demodicosis as the other major diagnosis in a puppy with multifocal hair loss, scaling and crusting, and pustular disease can mimic dermatophytosis. The exam is also when the in-contact animals get looked at. Wood's lamp examination: Worth stating precisely, because the myth in circulation is that only about half of Microsporum canis strains fluoresce. Merck cites an evidence-based review finding that 91-100% of untreated, infected animals will have glowing hairs. The technique matters: a plug-in lamp with built-in magnification, held within 2 to 4 cm of the skin, in a darkened room the user's eyes have adapted to, moving slowly from the head; only hair shafts glow apple green, not crusts, so crusts are lifted to look underneath. Fluorescence becomes less common as an animal recovers. Direct microscopic examination of hair and scale: Merck: hair and scales plucked and scraped from lesions and mounted in mineral oil can confirm infection in more than 85% of cases, and no clearing agent is needed. Infected hairs appear wide and pale against normal hairs that are thin and threadlike, with cuffs of spores on the outside of the shaft. This is a same-visit test with no laboratory fee. Fungal culture: Merck: sample only the lesions, not the whole coat, using a new unopened toothbrush brushed over the lesions and then inoculated onto dermatophyte test medium. Plates are incubated at room temperature, sealed in a bag, and examined daily for 14 days; pathogens are pale, never heavily pigmented. Merck warns that hair should not be wiped with alcohol first, because that can produce a false negative. PCR assay: Merck: confirms the presence or absence of fungal DNA on the coat, but cannot distinguish viable from non-viable spores, and needs more than 20 hairs and crusts submitted. Useful for confirming cure, with the caveat that dead spores still test positive. Skin biopsy: Merck: not indicated in routine cases, but indicated where there are nodular lesions or an unusual presentation. Merck's practical instruction is to tell the laboratory that dermatophytosis is on the differential list so special stains are used, and to submit several 8 mm punch samples or the whole nodule.
Does pet insurance cover ringworm in dogs (dermatophytosis)?
Dog Biopsy is normally covered by an accident-and-illness policy taken out before the signs started. A biopsy taken to investigate a new problem is covered by an accident-and-illness policy; a biopsy taken as part of routine screening is not. The pre-existing rule bites in an unusual way here, because the biopsy is often the moment a condition is formally diagnosed - if the lump or the sign was already in the record before enrolment, the biopsy that names it is still investigating a pre-existing condition.
What is the outlook for a pet with ringworm in dogs (dermatophytosis)?
Merck: dermatophytosis is a self-limiting disease that resolves without treatment in otherwise healthy animals, and resolution of infection takes 6 to 12 weeks. Treated, dogs are treated until mycological cure, which Merck puts at four to six weeks or more. Animals that are ill, stressed or have another underlying disease are harder to treat, partly because medicating them is harder and partly because they may not mount the cell-mediated immune response recovery depends on. In people, Merck notes the disease causes skin lesions that are easily treated. The two things that turn a straightforward case into a long one are stopping treatment on appearance rather than on a negative test, and treating one animal in a household where several are infected.
Can ringworm in dogs (dermatophytosis) be prevented?
Most of the practical prevention is grooming and household hygiene rather than avoidance. Merck's transmission mechanism points straight at it: contaminated clippers and the microtrauma they cause are an efficient route, so use a groomer that disinfects equipment between dogs. Isolate and test new arrivals, particularly kittens and puppies from shelters, hoarding situations or crowded breeding environments, which Merck names as higher-risk settings. Wash hands after handling a dog with any skin lesion, and take the household seriously - Merck classes this as a zoonotic disease. If a dog is diagnosed, clean mechanically first and use a bathroom disinfectant labelled effective against Trichophyton, and keep going until mycological cure rather than until the coat looks normal.
What does ringworm in a dog look like?
Ringworm is a fungal infection of the hair and the surface of the skin, and the name is the first thing that misleads. Costs for ringworm in dogs (dermatophytosis) run from $56 for routine vet checkup (wellness exam) to $1,110 for dog biopsy. A severe case can run past the top of that range — what treatment adds depends on how bad it gets.
What should I know about ringworm in dogs (dermatophytosis)?
Ringworm is a fungal infection of the hair and the surface of the skin, and the name is the first thing that misleads. Costs for ringworm in dogs (dermatophytosis) run from $56 for routine vet checkup (wellness exam) to $1,110 for dog biopsy. A severe case can run past the top of that range — what treatment adds depends on how bad it gets.
Is this actually a common disease?
Less common than the internet suggests. Merck puts true disease prevalence at under 4% of all skin disorders and states directly that it is not the most common skin disease of cats, contrary to what is reported in lay literature.
When does treatment actually stop?
Not when the coat looks normal. Merck's endpoint is both clinical cure — all lesions resolved and no new ones — and mycological cure, confirmed by a negative fungal culture or PCR, which it puts at four to six weeks or more.
Related conditions and costs
What treating it costs, procedure by procedure
- routine vet checkup (wellness exam) cost $56–$130 — The annual physical examination a healthy dog or cat gets - vitals, ears, eyes, mouth, coat and skin - priced as the exam fee alone, before any test or vaccine is added to the bill.
- dog biopsy cost $144–$1,110 — Taking a tissue sample from a dog and having a pathologist read it, priced from the laboratory fee upward rather than from a quote downward.
Related conditions
- symptoms of blocked anal glands in dogs — Two small scent sacs sit either side of the anus and normally empty when a dog passes a firm stool.
- dog colitis medication — Inflammation of the colon, which shows up as small, frequent, urgent stools carrying mucus and often fresh red blood, with straining.
- dog skin allergies — A lifelong immune reaction to ordinary environmental substances - pollens, moulds, dust mites, dander - that shows up as itching rather than sneezing.
- dog limping — Limping means something painful is interfering with the normal use of a limb, and Cornell's framing is that it deserves veterinary attention rather than a wait-and-see.
- staph infection in puppies — Crusty pustules on a puppy's hairless belly and groin, caused by the dog's own resident bacterium overgrowing.
- dog wound treatment — Cleaning and closing a wound is mostly a timing decision, and the two things owners get wrong are both correctable in the first hour.
- yeast infection in dogs — Malassezia pachydermatis is a yeast that lives on normal dog skin and in normal ears.
- dog skin yeast infection — Malassezia yeast lives on normal dog skin and only causes disease when something changes the skin it lives on.
- dog vomiting yellow — Yellow vomit is bile that has refluxed from the duodenum back into an empty stomach, and it is a description rather than a diagnosis.
- dog dementia treatment — An age-related degenerative brain disease that Cornell describes as causing deterioration similar to Alzheimer's disease in people, with beta-amyloid accumulating and neurons dying.
- dog coughing — A cough is a sign, not a diagnosis, and the same dry hack can come from an infection that clears itself in two weeks or from a failing heart valve.
- dehydrated dog treatment — Dehydration is not a disease, it is the measurable consequence of one, and the numbers behind it are published rather than guessed.
- dog diabetic symptoms — The pancreas stops making enough insulin, so glucose stays in the blood instead of feeding the cells, spills into the urine and drags water with it.
- dog diarrhea — Loose or watery stool, with or without blood, and the sixth most frequently recorded disorder in dogs in primary practice.
- dog ear infection treatment — Inflammation of the ear canal, almost always with a yeast or bacterial overgrowth on top of it.
- dog pregnancy symptoms — The signs owners read as pregnancy - weight gain, a swollen belly, mammary enlargement, milk, nesting behaviour - are produced just as reliably by a false pregnancy, and there is no home test that tells them apart.
- dog UTI symptoms — A bacterial infection of the bladder, usually Escherichia coli travelling up the urethra from the perineum.
- dog vomiting and diarrhea — Sudden vomiting, usually with diarrhoea, from an inflamed stomach and intestine.
- dog vomiting blood — Blood in a dog's vomit - fresh red, dark clots, or the brown grit that looks like coffee grounds because the stomach has already digested it.
- dog eye allergies — A red, weeping, itchy eye is what owners call an eye allergy, and environmental irritants and allergens genuinely are, in Merck's words, common causes of conjunctivitis in all species.
- hip dysplasia in dogs — An inherited malformation in which the hip joint is too loose, so the ball grinds in the socket and arthritis follows.
- ivdd in dogs — A disc between the vertebrae ruptures or bulges and presses on the spinal cord, causing pain, wobbliness or paralysis.
- worms in dogs — Four different worms with four different stories, grouped together only because they all live in a dog's gut.
- kennel cough in dogs — A contagious inflammation of the windpipe and airways caused by a mix of viruses and bacteria, not by one organism.
- parvo in dogs — A virus that destroys the lining of a puppy's intestine and the bone marrow that makes its white blood cells, producing vomiting and bloody diarrhoea that can kill in days.
- dog seizures — A burst of abnormal electrical activity in the brain, which in its classic form drops the dog on its side with stiff, paddling limbs, frothing, loss of consciousness and often loss of bladder and bowel control.
- kidney disease in cat symptoms — The kidneys lose function slowly and permanently, and the cruel arithmetic is that they hide it until most of them are gone.
- cat teeth disease — Three overlapping diseases, not one: gingivitis, which is reversible; periodontitis, which is not; and tooth resorption, in which the tooth dissolves from the inside out and which Cornell calls the most common cause of tooth loss in cats.
- signs and symptoms of cat diabetes — A disease in which the cat's cells stop responding properly to insulin, so glucose stays in the blood instead of feeding the body.
- why is my cat meowing so much — Excessive meowing is a sign, not a disease, and it is the sign this dataset can be most useful about — because its differentials range from a cat that has learned meowing produces breakfast to a male cat that cannot pass urine and will die within about two days without treatment.
- cat coughing — A cough in a cat is a lower-airway problem until proved otherwise, and the commonest cause is asthma - an allergic narrowing of the small airways that Cornell puts at 1 to 5% of cats.
- urinary blockage cat — A group of conditions causing painful, frequent, bloody or unproductive urination in cats.
- worm cat symptoms — Worms in cats are usually silent, and the signs owners are told to look for - a dull coat, a potbelly, vomiting, diarrhoea - are the same signs as a dozen other things.
Sources
Clinical sources
What this condition is, how it is diagnosed and when it becomes an emergency, from veterinary colleges, professional bodies and peer-reviewed primary-care studies.
- Dermatophytosis in Dogs and Cats — Merck Veterinary Manual, 2025.
- Diagnosis and treatment of dermatophytosis in dogs and cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology — Moriello KA, Coyner K, Paterson S, Mignon B; Veterinary Dermatology 28(3):266-e68, 2017.
Price sources
Where every figure in the cost section comes from. These are US fee schedules, published price surveys and carrier claims data — reported by us, and outside the scope of the clinical review noted at the top of the page.
- Veterinary Exam and Procedure Costs, including 50-state routine visit tables — CareCredit (Synchrony), 2025-2026 Synchrony Average Procedural Cost Study conducted by ASQ360 Market Research, 2026.
- Lack of online price transparency of small animal veterinary clinics in the United States — Adams, Gilley, Morris and Wisnieski, Frontiers in Veterinary Science, DOI 10.3389/fvets.2026.1788878, 2026.
- About Our Pricing — Cane Bay Veterinary Clinic, Summerville, South Carolina, 2026.
- Pricing and Transparency — Dallas Veterinary Clinic, Dallas, Texas, 2025.
- Veterinary Clinic Price List — Tequesta Veterinary Clinic, Florida, 2026.
- Philadelphia Pricing — Love City Vet, Philadelphia, Pennsylvania, 2026.
- Pricing — Kenmore Veterinary Hospital, Kenmore, Washington, 2026.
- Service Pricing — Covina Animal Hospital, Covina, California, 2026.
- Price List — Midvalley Animal Clinic, Taylorsville, Utah, 2026.
- Prices — Rocket City Mobile Vet, Huntsville, Alabama, 2026.
- Pricing — Modern Animal, 2026.
- Clinical Pathology and Histopathology Fee Schedule — Department of Veterinary Pathology, Iowa State University College of Veterinary Medicine, 2026.
- Canine Tests and Fees — Veterinary Medical Diagnostic Laboratory, University of Missouri, 2026.
- Animal Disease Diagnostic Laboratory Tests and Fees — Ohio Department of Agriculture, 2026.
- Pet Surgery Pricing — Veterinary Medical Center of Clayton, North Carolina, 2026.
- Lipomas in Dogs — Cornell Richard P. Riney Canine Health Center, Cornell University, 2026.