Diagnosing and Managing Ringworm in Dogs


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When I was in fifth grade, in a small rural school, there was a girl who just didn’t fit in. Today, I expect that she would be the target of cyber-bullying, with vicious Facebook posts from those of us who actually managed to read and write at grade level. But we didn’t have Facebook back then, so our venom was restricted to bathroom walls and schoolyard taunts.

See, Jenny was dirty. In the literal sense of the word. Once, to my eternal shame, I actually participated in tormenting her – I sat behind her in class, and one Friday afternoon when she draped her arm over my desk, I pulled out a ball-point pen and, without her realizing, made a little mark on her arm, just above the elbow. On Monday morning, I gleefully pointed out to all and sundry that the mark was still there – Jenny hadn’t washed over the weekend!

It gets worse. See, little a-holes that we were, we didn’t cut Jenny any slack over the fact that her family was poor. We made fun of her shabby clothes, her poorly cut hair, and her paralyzing shyness (which was probably due in no small part to our continual harassment). And then, one day, when she came to school with round, red lesions on her arms and legs, it was open season on Jenny – but from a distance, because we knew what those marks meant. Jenny had ringworm. Worms! Horrible, nasty, round, squirming worms burrowing under her skin.

What is Ringworm?

Not only were we little a-holes, we were ignorant as well. Not in the sense that the word is often used as a synonym for being rude (although we surely were exactly that), but in the sense of “not knowing.” We didn’t know that ringworm is actually not a worm infestation at all – it’s actually a fungus. Those round lesions are inflamed areas caused by a group of fungi known as dermophytes, not by worms.

Can I Catch Ringworm From My Dog?

Yes, you can. There are numerous dermophytes, some of which will attract just one species. Others are zoonotic, meaning that more than one species can be infected. The dermophytes that cause ringworm in dogs (microsporumcanis, microsporumgypseum and trichophytonmentagrophytes) are zoonotic. So ringworm in dogs is most definitely transmittable to humans, and to other pets as well.

What Does Ringworm in Dogs Look Like?

Ringworm in dogs looks much the same as ringworm in humans – it appears as roundish lesions on the skin. This is because the fungi that cause ringworm stays alive by consuming keratin, which is a substance in the skin’s outer layers. The process causes hair shafts to break, leading to a roughly circular pattern in the affected area. As the condition worsens, the lesions may lose their pattern and spread out, leading to large, hairless, reddish patches. As if this isn’t ugly enough, the fungus may begin to die back in the area that was originally affected, and hair will regrow there. This results in tufts of hair surrounded by scabby skin. With ringworm in dogs, the infection may also spread to the nails, which will become dry and rough, and ultimately become so brittle that they break. Needless to say, this can be painful for the dog.

How Does Ringworm Spread?

Coming into contact with the fungus that causes ringworm does not necessarily mean that the infection will be transmitted. The overall health of the dog (or the person) is a factor, as is the age of the potential host. A healthy adult human, for instance, may very well resist contracting ringworm, even if exposed to a carrier, if there are no points of entry like cuts or scrapes in the skin. On the other hand, a child, an elderly person with a suppressed immune system, or a pet in poor condition might conceivably pick up the fungus even in the absence of obvious open areas in the skin.

Ringworm can also be transmitted by touching anything that the contaminated host may have come into contact with. So if you comb a dog that has ringworm, and then use the same comb to groom another pet, you can transfer the fungus and infect that pet.

How Quickly Does Ringworm in Dogs Spread?

Ringworm, in dogs and in humans, is an insidious thing. It takes quite a while to develop – seven days at minimum after the host is exposed to the fungus before the lesions appear, and often up to 21 days. In some cases, there may never be obvious signs of ringworm in dogs, but the animal will still have the condition, and will still be able to transmit it to other dogs, other pets, and humans.

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How is Ringworm in Dogs Diagnosed?

The most obvious method of diagnosing ringworm in dogs is to look for the skin lesions. However, there are other conditions that can lead to lesions, so a visual examination is not the most reliable method.

If you suspect that your dog has ringworm, your veterinarian can use an ultraviolet light to examine the dog’s skin. Most types of ringworm will glow yellowish-green when exposed to ultraviolet light in a darkened room. This method isn’t infallible, though, as some types of ringworm fungus will not fluoresce (most notably microsporumgypseum and trichophytonmentagrophytes), while certain topical preparations that you might be using to ease your dog’s skin irritation could also result in a “false positive” for ringworm.

In order to provide a proper diagnosis, your veterinarian will want to take a skin sample. Usually, ringworm can be diagnosed or ruled out quickly, but if the fungus is slow to grow, your vet may not be able to give you a conclusive answer for about a month.

How is Ringworm in Dogs Treated?

Notice, please, that I said “how,” and not “when.”Not treating ringworm in dogs is never an option, even if the case isn’t all that severe. This is because, as I’ve already pointed out, the condition is zoonotic – it can be transmitted to other pets and to humans. Treatment is essential, especially if you have children or elderly people in your household.

You can treat ringworm in dogs by means of topical therapy and/or oral therapy. However, whether you choose one or the other, or a combination, it’s very important that you clean up your environment in order to prevent further infestations.

1. Topical Therapy

Topical therapy is the use of an ointment or cream applied to the areas that are affected by ringworm. In dogs, this can be difficult. Long-haired dogs will need to be clipped or shaved before applying the topical preparation, and bathing before application is strongly advised. Although I’ll talk about holistic remedies in a bit, I think that the best course of action is to go with whatever topical preparation your veterinarian recommends. For topical treatment to work on ringworm in dogs, it will usually need to be used for several weeks, and in severe cases, possibly months.

You will need to bathe your dog before using topical preparations, and also thoroughly clean any areas that your dog may have come into contact with (see “Environmental Cleaning”).

2. Oral Therapy

Most cases of ringworm in dogs will also require the use of an anti-fungal drug, administered orally. Historically, the preferred treatment has been a drug called griseofulvin, but if your vet is using this, he or she may be “old school.” There are newer drugs available, like terbinafine and itraconazole, which have been proven to have fewer side effects. If your vet recommends griseofulvin, make sure to ask why.

Usually, oral therapy needs to be administered for at least six weeks in order to prevent the ringworm from recurring. Sometimes, a longer treatment is warranted. Your vet will usually take a ringworm culture every two weeks to determine how the treatment is going. Two consecutive treatments showing no ringworm generally means that the condition is under control, although your vet will still likely recommend continuing for the full six weeks.

3. Environmental Cleaning

As is the case with virtually any contagious illness, the most important thing is to remove the source of the contagion from the environment. If you have other pets, try to keep the dog away from them for a while. I know that this can be difficult – you might be saying, “But Dallas always sleeps with his kitty!” But you don’t want kitty to get ringworm, do you? So separate them for now, and think about how happy they’ll be when they’re finally back together!

Now, get out your disinfectant – Dettol is a good one – and go to work cleaning all the surfaces that your dog might have been in contact with. If you’re like me, your dog has probably had the run of the house, so I know it’s going to be a big job, but you have to do it.

You should also go aboard any upholstery, because ringworm can be transmitted in pet hair. Use a good hand-held vacuum cleaner, but keep in mind that even the best vacuum isn’t going to get all the loose hair. Then you can use duct tape wrapped around your hand, sticky side out, to get what’s left. Then spray with a good, pet-safe disinfectant to complete the job.

If you’re anything like me, I know you probably hate housework, but when you’re dealing with ringworm in dogs, you have to be extremely vigilant. So buckle down and do it, for the sake of your dog, your other pets, and your family members.

Diagnosing and Managing Ringworm in Dogs

How Long Does Ringworm in Dogs Stay Contagious?

Putting it this way, ringworm likes to hang around. If your dog has ringworm, he can be contagious for approximately three weeks, even if you go with topical and oral treatment combined, and clean vigorously. If you don’t complete the treatment, and if you decide that “clean enough is good enough,” you are running the risk of continuous exposure to other pets and family members.

Will My Dog Get Better?

Okay, I know I’ve been talking gloom and doom here, but the fact is that almost all dogs, provided they get proper treatment, will recover 100% from a ringworm infestation. The only situation in which there might be complications would be if the dog has an underlying condition that compromises his immune system. Even then, with aggressive treatment, the likelihood is that the dog will enjoy a full recovery.

Holistic Remedies

If you’re a regular reader, you know that I’m a big believer in doing what your veterinarian recommends. There are holistic remedies for ringworm in dogs, though, and if your vet is fine with any of the following, then so am I.

1. Tea Tree Oil

Tea tree oil has been used worldwide for centuries for its anti-viral and anti-bacterial properties. It’s worth noting, though, that it’s generally recommended as a preventative treatment, not a cure. In other words, applying tea tree oil to your dog’s skin might work to prevent ringworm, but once ringworm takes hold, tea tree oil is not a cure.

2. Garlic

Garlic is one of those “iffy” remedies. It contains a substance known as ajoene, which works to combat various types of fungi. Some holistic practitioners recommend cutting a clove of garlic in half and rubbing it on the affected area. However, this will only kill the ringworm fungus for about 12 hours, and given that we’ve already talked about how long the fungus can live, I’d question the efficacy of this method.

3. Apple Cider Vinegar

Apple cider vinegar has often been touted as a cure-all for just about any type of skin disorder you can imagine. Speaking from experience, I can tell you that it was the only thing that eased my discomfort from a nasty case of chicken mites back in my “I wanna live off the land and eat only my own organically raised eggs” days. The catch here is that when it comes to ringworm in dogs, it’s strictly preventative – you’ll have to bathe your dog regularly, and rinse using a solution of apple cider vinegar. Once your dog actually has ringworm, apple cider vinegar is not a cure.

4. Basil

Basil has been used for a long time, by our ancestors in soaps, perfumes and toothpastes. It’s also known to be a powerful anti-fungal agent, when applied to the skin. However, I have to tell you that none of my research has shown that it will cure ringworm.

5. Neem Oil

Neem oil comes from the neem tree, and has long been proven to be toxic to various fungi, including those that cause ringworm in dogs. It’s believed to act against the fungi if applied directly to the skin, but some dogs may be sensitive to it. To prevent irritation, use it sparingly or combine it with a carrier like olive oil.  Neem oil can be toxic if ingested, but since it tastes very bitter, it’s not likely that your dog will want to lick it. If he does, discontinue use immediately.

6. Bastard Teak

Stop giggling. Right now. I mean it! This unfortunately named substance comes from another tree, the bastard teak, which grows in India. The seeds of the bastard teak, if ground up in olive oil or lemon juice and applied to ringworm 3 times daily, are believed to destroy the infection. Of course, as I said before, I’m a huge believer in veterinary medicine, so take note of the phrase “believed to.”

7. Licorice

That said, I do know that many of our modern medicines are based in herbal preparations, so I’m flexible. And, I think, onside with the idea of licorice as a remedy for ringworm in dogs. I wouldn’t advise that you feed your dog licorice – in fact, I wouldn’t recommend feeding anyone licorice – personally, I hate the taste. But if you buy licorice at a health food store, grind it up and mix it with water, you can apply the solution to your dog’s skin. It’s been show to inhibit a lot of fungi, including microsporum.

8. Oregano

You’re probably most familiar with oregano as an herb used in Italian cuisine. What you might not know is that it contains thymol, which is known to inhibit fungal growth. Mix a couple of drops of oregano oil in approximately a teaspoon of pure coconut oil, and apply it to your dog’s skin. It might work to counteract the ringworm, and if it doesn’t, you can always go back to modern veterinary methods knowing that there is nothing in the oregano preparation that will cause your dog any harm.

9. Aloe Vera

You have probably used aloe vera yourself, in skin creams or shampoos. The extract of the aloe vera plant is very soothing, and although it won’t actually destroy the fungi that cause ringworm in dogs, it will definitely soothe your dog’s skin and give him some relief from the discomfort that the ringworm infestation causes.

Now, having dealt with holistic remedies, I want to go back to what you can do to make sure a ringworm infestation doesn’t recur. You’ve treated the infection, and you’ve cleaned, but there’s something else you might not have considered.

Where Does Ringworm Hide?

How many toys does your dog have? Quick, now, just answer. Three? Five? Eleven? Too many to count?

That’s what I thought – if you’re anything like me, there are dog toys all over the house. Too many to count. And every single one of those toys can harbor the ringworm fungus.

Now, does your dog share his toys with other pets? With your kids? Does your dog leave his toys around the house on rugs and furniture?

You know where I’m going with this. Those toys are going to spread ringworm. So take them away.

Oh for heaven’s sake, stop! Just take them away for a while and quit looking at me like that – I’m not a monster that’s going to suggest depriving your dog of everything he loves, okay? Just take all those toys and wash them in very hot water. Then soak them in a bleach solution for about 15 minutes, and wash them again. Once you’ve done that, you can give them back to your dog. If you think he’s going to be devastated at having his toys taken away, go down to the pet supply store and buy him a brand new toy to distract him while his old toys are being cleaned. Or even better, just throw all the rubber toys in the dishwasher, the “stuffies” in the washing machine, and take him outside and play with him while his toys are being cleaned – he’ll be so happy to be playing with you that he won’t even miss his toys! And if you’re wondering how best to deal with the cleanup, check out my post about dealing with dog laundry.

The Final Word

Ringworm in dogs is not a pleasant thing to have to deal with, but it’s not the end of the world either. Unless a dog is very ill to begin with, he will bounce back quite nicely from a bout with ringworm. You can try holistic methods to prevent ringworm, although most won’t be a cure – you will actually need medication from your vet to make your dog feel better.

The main thing is to eliminate ringworm as soon as you find it. Then clean up your home to prevent recurrences. If you have other pets in the household, you might need to keep them away from the infected dog for a while, but they’ll soon be back together.

As for me, I’d like to get back together with Jenny. Or maybe I should say “together with Jenny” since we were never together back in the day – because I was one of those a-holes I told you about. I’ve been trying to find her on social media so I can apologize for my part in the way she was treated. And Jenny, if by some fluke you’re reading this, I am so very, very sorry. I wish I could take it all back, and I hope you can somehow forgive me.

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