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All About Ringworm In Dogs

Ringworm in dogs is not caused by worms but by a fungus, which makes it a fungal infection rather than a parasitic one.

The fungi involved are called Dermatophytes and in dogs there are three different strains which can cause ringworm.

Guide to ringworm in dogs

The most common one is Microsporum of the Canis variety (aka M. Canis), which causes somewhere between 70% - 90% of cases.

It's a very contagious 'zoonotic' condition (which means that it can be transmitted from one species to another).

Although ringworm is most common in cats, many different animals can catch it, including dogs, cats, humans, horses and cows.

If you come in contact with a pet or other animal (or person) who has Ringworm, you are at risk of catching it too.

It's the fungal spores which spread the infection, and they can be transmitted either by direct skin-to-skin contact, or by coming in contact with anything which has been contaminated by those spores.

Bedding, clothes, toys, clothes, dishes, furniture, carpets, hard flooring, soil.... just about any surface can harbor these spores which is why it's so infectious.


Ringworm Symptoms in Dogs

There is at least one part of this conditions' name which is correct - the 'ring' part!

The most common symptoms of ringworm in dogs is the development of circular scaly, bald spots.

Most dogs start off with just a single lesion and sometimes this isn't noticed or is ignored.

Not every dog will show exactly the same type of skin lesion, and as the disease progresses the look of the irritation will change and it will spread.

The skin where the hair has been lost may be pink, reddened, scaly, crusty or irritated. It can also be itchy.

Often the outer edge of the circle will show the most irritation, scaling or crusting and the center will be more paler and smoother, but sometimes the center of these areas will look red and/or irritated.

The fungal spores actually live in the hair follicle (which is right at the root), this causes individual hairs to thin, break or fall out completely, forming the characteristic bald spots. 

If the patches are unevenly shaped, either Ringworm is not to blame, or you're seeing where two or more lesions have joined together.

The incubation period for ringworm in dogs is approximately 10 days.

This means that it will be about 10 days from the contact with the fungus before Fido will show symptoms.

These lesions/patches usually appear first on your dogs' head, ears, tummy, tail, paws or on his sides - however they can show up just about anywhere.

If the condition isn't diagnosed and treated, these patches can become very widespread, even covering your dogs' entire body. 

Any dog can catch ringworm, but young puppies and dogs whose immune system is weakened by age, illness or stress, are most susceptible.

Ringworm is a common cause of hair loss in puppies.

As with many other dog illnesses and conditions, some puppies or dogs will catch Ringworm without developing any symptoms. They will still be contagious and are 'carriers' of this condition.


Diagnosing Canine Ringworm

Often a veterinarian can diagnose Ringworm in dogs simply by a physical examination. 

Ringworm on dogs' muzzlePhoto Attribution: Washington State University

But to be sure there are tests which can be done to verify that visual diagnosis.

These include looking at your dogs skin using an ultra-violet light source called a 'Woods' Lamp', or by performing certain tests on your dogs' hair.

The Woods Lamp only shows a positive diagnosis for the M. Canis spores (the fungus will glow a bright green), but even then it's only accurate about 50% of the time. A false-negative result is very real possibility.

If your dog is infected with one of the other strains he'll also test negative with the Woods Lamp, so other tests are usually needed to be certain of the correct diagnosis.

These involves laboratory testing of hair samples, but the results can take anywhere from one to two weeks, so treatment is often started anyway if your veterinarian is confident that Ringworm is causing your dogs' symptoms.

Your dog is contagious while he has an active infection (and can still be contagious for some time after symptoms disappear).

It's best to keep Fido away from other dogs for several weeks once he's been diagnosed with Ringworm and treatment has been started.


Ringworm Treatment For Dogs

Anti-fugal treatments are used to knock out this infection.

Depending on how early your dog is diagnosed and how severe the problem is he may be treated with medicated shampoos, dips or topical treatments.

These products might contain Miconazole, Chlorhexidine or Lime Sulfur.

Sometimes oral medications are needed too.

A medication called Griseofulven is still the most commonly prescribed treatment and it can be very effective.

However, it can have some fairly serious side-effects so should only be used in severe cases and you'll need to keep an eye on your dog for any side effects which could spell trouble.

Side effects of Griseofulven in dogs can include:

  • Nausea (often exhibited as excessive drooling/salivation and yawning)
  • Vomiting
  • Diarrhea
  • Lethargy
  • Loss of appetite
  • Anemia

Vomting and/or diarrhea should be taken seriously as they show the medication is causing digestive upset.

If your dog suffers from either of these symptoms discuss it with your veterinarian as he/she may want to choose a different medication.

Sometimes Griseofulven can cause liver damage which is potentially very serious.

Yellowing of the gums, eyes or skin could mean that your dogs liver is being affected and warrants an immediate vet consult.

Pale gums or tongue could indicate anemia, and also needs quick veterinary attention.

If your pooch is prescribed this medication make sure you follow your veterinarians' instructions about dosage etc. very carefully.

Itraconozole is becoming a more frequently prescribed alternative oral medication, as it has less side effects.

In most cases the treatment begins to work within 7 to 14 days and you should start to see the patches begin diminish in size, the irritation start to fade and signs that the hair is growing back - albeit slowly.

If Fido is being treated for ringworm and you don't see any improvement by the end of two weeks, take him back to your veterinarian for another evaluation. 

Sometimes the treatment needs to be 'tweaked' or changed.

Also, please don't stop your dogs' treatment until your veterinarian says you should. 

The symptoms usually become undetectable (ie it looks like Fido is 'cured') before all the fungi have been eradicated.

If you stop the treatment at this point chances are very good that the fugus will start growing and multiplying again and you'll be right back where you started fairly quickly.

Always finish all the medication or treatments that have been recommended/prescribed by your vet.


Natural Treatment For Ringworm in Dogs

If you catch the outbreak of ringworm quickly, and your pooch is in good overall health, you may be able to stop it in it's tracks with natural treatment options.

The most popular, and effective, choice is Naturasil Ringworm Treatment.


Ringworm Pet by Naturasil

A homeopathic treatment made from 100% natural extracts.

This Lime-Sulfur concentrate should be mixed with shampoo (full instructions included) and applied, allowed to soak into fur and skin, then rinsed thoroughly.

This process needs to be repeated every 5 - 6 days for several weeks.

A gentle treatment that is chemical free and has no side-effects.

However if your pup/dog has a moderate to severe ringworm problem, or if after two weeks of using Naturasil you don't see any improvement, I'd recommend having your dog examined by your veterinarian again.

Naturasil - Herbal Pet Shampoo

A gentle, natural, organic shampoo suitable for dogs, puppies, cats & kittens.

Recommended for use with Naturasil Ringworm Concentrate (above).


Vet Basics Lime Sulfur Dip

Gentle, natural antimicrobial shampoo recommended for use against Ringworm, Mange and Lice.

Designed to be diluted with water and sponged on.

Effective and affordable.


Warning: Lime-Sulfur Has A Very Strong Smell!

Lime sulfur is a very effective treatment for ringworm, mites and several other skin conditions. It smells like rotten eggs, but this odor does fade given a little time. I think it's a small price to pay if it works.


Preventing Ringworm Re-infestation

Because ringworm in dogs is so easily transmitted, it's very important to make sure that you're thoroughly sanitize all the possible places which could be harboring fungal spores.

A 1:10 solution of bleach and water will kill the spores and can be used to clean toys, bowls, hard flooring and surfaces, cement, brick and so on.

Obviously it's also really important to rinse carefully anything that might come in contact with your dogs' mouth.

A Chlorhexidine Disinfectant is also effective used as an all-purpose cleaner.

Soft toys, bedding and clothing should be washed on the hot cycle (and add bleach to any loads which can handle it).

Steam clean your carpets and rugs, the hot water and cleaning agents should get rid of those pesky spores.

High standards of personal hygiene among the human family members is very important if a family pet has been diagnosed with ringworm.

If any family member develops circular, reddened, itchy or scaly areas on their skin, it's important to have them examined by a doctor.

Prompt treatment will eradicate the infection and prevent it from spreading. However, as with dogs the treatment can take some time to completely eradicate the fungus.

My daughter caught ringworm once, after a visit to the local city pound, and was prescribed a topical anti-fungal cream which did, eventually, fix the problem.


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