Ringworm in Dogs Treatment (UK Guide): Shampoo & Home Decontamination

Ringworm in Dogs: Shampoo Treatment & Home Care

Ringworm in dogs is a highly contagious fungal infection that spreads easily to humans, especially children and vulnerable people. It's not a worm—it's a fungus that attacks the skin, hair, and nails, and it requires immediate action because the spores can survive in your home for up to 18 months.

Here's what makes ringworm particularly challenging: even if your dog only has small patches of hair loss, they're shedding infectious spores onto every surface they touch. Your carpets, sofa, bedding, and even your clothes can harbour the fungus for months. Treatment needs to tackle both the infection on your dog and the contamination in your environment, or you'll be fighting a losing battle with re-infection.

This guide covers everything you need to know about treating ringworm at home, from the correct way to use medicated shampoo (spoiler: most people don't leave it on long enough) to the proper decontamination protocol that actually works. We'll also explain why your vet's diagnosis is essential before you start treatment, and what "cure" really means when it comes to ringworm.

What Ringworm Actually Is (and Why It Spreads So Fast)

Ringworm is a fungal infection officially called dermatophytosis. The most common culprit in dogs is a fungus called Microsporum canis, which causes about 70% of cases.^[1] It targets the outer layers of skin, hair shafts, and sometimes the nails.

The "worm" part of the name comes from the circular rash it causes in humans, but there's no parasite involved—just a stubborn fungus that's extremely good at spreading. Dogs and cats are the main carriers, but the infection readily jumps to humans through direct contact or by touching contaminated surfaces.

Why This Isn't About Poor Hygiene

Ringworm has nothing to do with how clean your home is or how well you care for your dog. Fungal spores are everywhere in the environment, and infection happens when your dog comes into contact with them at the wrong time. Even immaculately kept homes can have ringworm outbreaks if a dog brings the fungus in from outside.

Puppies, elderly dogs, and those with weakened immune systems are most vulnerable because their bodies can't fight off the infection as effectively.^[2] Long-haired breeds may also be more prone simply because the fungus has more hair to attach to.

The Real Risk: Transmission to Humans

Ringworm is zoonotic, which means it passes from animals to people, and it does so readily. Children are particularly at risk because they tend to have closer contact with pets and may not be as careful about washing their hands afterwards.^[3]

Vulnerable groups—including the elderly, pregnant women, and anyone with a weakened immune system—can develop more severe infections. In humans, ringworm typically appears as circular, red, itchy patches with raised, scaly edges. If it gets onto the scalp, it can cause hair loss.

This is why immediate action matters. It's not just about treating your dog—it's about protecting your family from a condition that can spread through your entire household.

How Long Spores Survive (Longer Than You'd Think)

The most frustrating thing about ringworm is the sheer resilience of its spores. Fungal spores can remain infectious in your home environment for 18 to 24 months, clinging to carpets, furniture, bedding, and even floating in the air.^[4]

This means that treating your dog alone isn't enough. If you don't simultaneously tackle environmental contamination, your dog will keep getting re-infected from the spores they shed weeks ago. You'll think the treatment isn't working when actually, you're just dealing with re-infection from your own carpets.

Spotting the Signs: What Ringworm Looks Like

The classic sign of ringworm is patchy hair loss, often starting as small, scaly bald spots that expand over time. These patches are commonly found on the face, ears, paws, and limbs, though they can appear anywhere on the body.^[5]

Here's what to look for:

• Circular or irregular bald patches - Hair loss that might start small but spreads outwards
• Scaly, crusty skin - The affected areas often have a grey, flaky appearance with crusting in the center
• Red, inflamed skin - The lesions may be raised and slightly red around the edges
• Brittle hair - Infected hair shafts break easily, leaving stubby patches
• Nail problems - In some cases, the infection affects the claws, causing them to become brittle, thickened, or even fall off
• Itching (sometimes) - Not all dogs itch, but some will scratch at the affected areas

Despite the name, ringworm in dogs doesn't always form the neat circular "ring" pattern you see in human cases. The lesions can be patchy, irregular, or scattered across different parts of the body. This is why visual diagnosis alone doesn't work—you need proper testing.

Why Your Vet's Diagnosis Isn't Optional

If you suspect ringworm, contact your vet immediately—don't wait to see if it clears up on its own. Many skin conditions look similar to ringworm (bacterial infections, allergies, mites), and using the wrong treatment wastes time while the infection spreads.

Vets use several diagnostic methods to confirm ringworm:^[6]

• Wood's Lamp examination - A UV light that makes some strains of Microsporum canis glow apple-green. Quick and useful, but only about 50% of ringworm cases show this fluorescence, so a negative result doesn't rule it out.
• Fungal culture - The gold standard test. Your vet takes hair and skin samples and grows them in a lab to see if fungus develops. Results can take 10-14 days, but this test reliably confirms the diagnosis and identifies the exact fungus involved.
• PCR testing - A newer, faster test that detects fungal DNA. Results come back within days, which is helpful for starting treatment quickly. The downside is that PCR can remain positive even after the fungus is dead, so it's less useful for confirming cure.

Your vet will prescribe a combination of treatments based on the diagnosis. Don't try to treat ringworm with over-the-counter products or home remedies—you'll likely make things worse or prolong the infection.

What to Tell Your Groomer

Groomers have a legal and professional responsibility to protect their staff and other clients' pets from contagious conditions. If your dog is suspected of having ringworm, reputable groomers will refuse service until you provide veterinary clearance confirming the infection has been successfully treated.

This isn't personal—it's about biosecurity. One infected dog in a grooming salon can contaminate the entire facility and spread the fungus to dozens of other pets. Be honest with your groomer about your dog's health status, and they'll work with you to reschedule once treatment is complete.

Medicated Shampoo Treatment: The 10-Minute Rule

Treating ringworm successfully requires both oral medication (prescribed by your vet) and topical treatment with medicated shampoo. The oral medication fights the infection from the inside, while the shampoo tackles it from the outside and—crucially—reduces the number of infectious spores your dog sheds into your home.

This combination therapy typically runs for 6 to 12 weeks, and you must not stop early just because the visible lesions have healed. Stopping prematurely almost guarantees the infection will come back.

What Makes Antifungal Shampoo Work

Vet-prescribed medicated shampoos for ringworm typically contain a combination of miconazole nitrate (2%) and chlorhexidine (2%). Miconazole is the antifungal agent that kills the dermatophyte fungus, while chlorhexidine provides additional antimicrobial action and helps clean the skin.^[7]

Products like Malaseb are commonly prescribed in the UK. These are prescription-only (POM-V), which means you can't buy them over the counter—your vet must provide or recommend them after confirming the diagnosis.

The Single Most Important Instruction: 10 Minutes Contact Time

Here's where most people go wrong: medicated shampoo must stay on your dog's coat and skin for a full 10 minutes before rinsing.^[8] If you rinse it off sooner, the active ingredients don't have time to work, and you're essentially just giving your dog a regular bath.

This contact time isn't a suggestion—it's the difference between effective treatment and wasted effort. Set a timer, keep your dog calm (easier said than done), and make sure the lather stays on for the full duration.

How to Use Medicated Shampoo Properly

Follow these steps for each treatment:

1. Wet your dog thoroughly - Use lukewarm water to wet the entire coat down to the skin.
2. Apply the shampoo generously - Work it into a thick lather covering the entire body, including hard-to-reach areas like under the tail, between the toes, and around the face and ears. Don't just focus on visible lesions—treat the whole dog.
3. Start your timer for 10 minutes - This is non-negotiable. Keep the lather on for the full contact time.
4. Keep your dog calm and wet - If the lather starts to dry out, add a bit more water to keep it active. Distract your dog with treats or calm talking.
5. Rinse thoroughly - After 10 minutes, rinse all the shampoo out completely. Leftover product can irritate the skin.
6. Dry carefully - Use towels that you'll wash immediately afterwards on a hot cycle, or designate specific "ringworm towels" that you'll disinfect or discard after treatment ends.

Treatment frequency is typically twice weekly, but follow your vet's specific instructions. Some cases need more frequent bathing, particularly in the early weeks.

Clipping and Pre-Treatment

For dogs with widespread or severe infections, your vet may recommend clipping the coat short before starting shampoo treatment. This serves two purposes: it removes infected hair shafts that act as reservoirs for the fungus, and it allows the medicated shampoo to reach the skin more effectively.

If clipping is recommended, have it done by your vet or under veterinary supervision—don't attempt this at home unless instructed. Clipping spreads spores everywhere, so it needs to be done in a way that minimizes environmental contamination.

Protect Yourself During Treatment

Every time you handle your infected dog or apply treatment:

• Wear disposable gloves - Nitrile gloves work well and should be thrown away after each use
• Wear old clothes or an apron - Clothes that you can wash immediately on a hot cycle
• Wash your hands thoroughly - Even if you wore gloves, wash your hands and forearms with soap and warm water afterwards
• Keep children away - Don't let kids help with treatment or handle the dog until the infection is cleared

The shampoo treatment isn't just about curing your dog—it's about preventing the infection from spreading to you and your family.

Environmental Decontamination: The Part Most People Get Wrong

Treating your dog without decontaminating your home is like bailing water from a sinking boat without fixing the hole. The spores your dog has been shedding for days or weeks are embedded in carpets, furniture, bedding, and every surface they've touched. If you don't tackle this contamination, re-infection is almost guaranteed.

Environmental decontamination requires a systematic approach. There are no shortcuts, and regular household cleaners won't do the job.

Step One: Isolate Your Dog

Until the infection is cured, restrict your dog to areas that are easy to clean—ideally rooms with hard floors like tile, vinyl, or laminate. Keep them out of carpeted rooms, off soft furnishings, and away from communal bedding areas.

This containment strategy has two benefits: it limits the spread of new spores, and it makes your decontamination job manageable. You can't effectively clean an entire house, but you can thoroughly decontaminate a utility room and kitchen.

The Two-Step Cleaning Protocol

Effective decontamination requires two distinct steps, in this order:

Here's what physical removal looks like:

• Vacuum thoroughly and frequently - Vacuum all carpets, rugs, soft furniture, and high-traffic areas daily if possible. Focus on areas where your dog spends time. The goal is to remove infected hairs and skin debris before they embed deeper into fabrics.
• Dispose of vacuum contents immediately - Empty the canister or throw away the bag straight into an outside bin. If you leave it in the vacuum, you'll aerosolize spores the next time you use it.
• Steam clean carpets and upholstery - Steam cleaning helps loosen and remove embedded spores. The heat also helps kill some of the fungus, though it's not a complete solution on its own.
• Wash all soft items - Dog bedding, blankets, towels, and any washable items should go through the longest washing cycle your machine offers, using the hottest water safe for the fabric (ideally above 43°C/110°F).^[10] Better yet, consider discarding heavily contaminated items like old dog beds.

Disinfectants That Actually Work

You have two main options for disinfecting hard surfaces:

Household Bleach (Sodium Hypochlorite): Effective on bleach-safe hard surfaces when diluted correctly. Use a ratio of 1 part bleach to 10 parts water (or a more dilute 1:32 for surfaces that might be damaged by stronger concentrations).^[11]

The critical part is contact time: leave the bleach solution on the surface for at least 10 minutes before wiping. Bleach also corrodes metal and can discolour fabrics, so use it carefully and only on appropriate surfaces.

Veterinary-Grade Sporicidal Disinfectants: Products like F10 SC Veterinary Disinfectant are specifically designed to kill resistant pathogens including ringworm spores. For ringworm, use the high-level disinfection dilution rate of 1:100 (10ml per litre of water) with a contact time of at least 15 minutes.^[12]

F10 is available through veterinary suppliers and some pet retailers in the UK. It's more expensive than bleach but safer for a wider range of surfaces and less likely to cause irritation.

What to Clean and How Often

During active treatment, clean and disinfect at least weekly, or more often if you have time:

• Hard floors - Sweep or vacuum, then mop with bleach solution or F10, allowing proper contact time
• Furniture surfaces - Wipe down with disinfectant, particularly items your dog has contact with
• Food and water bowls - Wash daily and sanitize with bleach or F10
• Toys and accessories - Discard porous items, disinfect hard plastic or rubber toys
• Grooming tools - Soak brushes, combs, and clippers in disinfectant after each use

Yes, this is exhausting. But it's the only way to break the re-infection cycle and ensure your dog actually gets better.

Confirming Cure: When Is Treatment Actually Finished?

Here's the hardest part: visible lesions clearing up does not mean your dog is cured. The skin might look normal and the hair might be growing back, but your dog could still be carrying viable fungal spores that will re-infect them or spread to family members.

This is called "clinical cure" (the symptoms are gone) versus "mycological cure" (the fungus is actually dead). You need mycological cure, not just clinical cure.

The Gold Standard: Fungal Culture Testing

The only reliable way to confirm cure is through two consecutive negative fungal cultures taken several weeks apart.^[13] Your vet will take hair and skin samples and grow them to check for fungal growth.

The typical protocol is:

• Continue all treatment (oral medication, topical shampoo, environmental decontamination) until clinical signs disappear
• Submit a fungal culture sample 2-4 weeks after clinical cure
• If negative, submit a second culture sample 2-4 weeks later
• Only stop treatment after two consecutive negative results

This process usually means treatment runs for 6-12 weeks total, sometimes longer for severe cases. It feels excessive when your dog looks healthy, but cutting corners leads to relapse. Given the cost of treatment including multiple fungal cultures and extended medication, having proper pet insurance can help ensure you complete the full treatment course.

Prevention: Avoiding Re-Infection

Once you've finally cleared ringworm, the last thing you want is to go through it again. Here's how to minimise the risk:

• Quarantine new pets - Don't bring new dogs or cats into your home until they've been cleared by a vet. Ringworm is particularly common in young animals from shelters or breeding facilities.
• Regular grooming and hygiene - Keep your dog clean and check their skin regularly. Early detection makes treatment far easier.
• Disinfect grooming tools - Clean brushes, combs, and clippers after each use, especially if you groom multiple pets.
• Wash bedding regularly - Hot water washing of dog bedding helps reduce the environmental spore load even when there's no active infection.
• Monitor your own skin - If you notice circular, scaly, red patches on your skin after handling your dog, see your GP. Early treatment for humans is simple and effective.

Ringworm is frustrating and time-consuming to treat, but with systematic treatment, thorough environmental control, and patience, you will get through it.

Frequently Asked Questions

References

This guide is based on verified veterinary and medical sources:

• [1] MSD Veterinary Manual - Dermatophytosis in Dogs and Cats
• [2] PDSA - Ringworm in Dogs
• [3] CDC - Ringworm Risk & Prevention
• [4] VCA Animal Hospitals - Ringworm in Dogs
• [5] The Kennel Club - Ringworm in Dogs
• [6] Veterinary Partner (VIN) - Ringworm in Dogs and Cats
• [7] VetUK - Malaseb Medicated Shampoo
• [8] UK Pet Drugs - Malaseb Clinical Particulars
• [9] Austin Animal Services - Ringworm Environmental Decontamination
• [10] University of Wisconsin Shelter Medicine - Ringworm Guidelines
• [11] Cats Protection - Ringworm Guidelines
• [12] F10 Products UK - F10 SC Veterinary Disinfectant
• [13] Today's Veterinary Practice - Diagnosing and Treating Dermatophytosis