Yeast Infection in Dogs: How to Recognize Malassezia and What Actually Helps?

Yeast overgrowth can be one of those problems that looks very much like an allergy from the outside. The dog scratches, licks its paws, the ears become red or dark, the skin turns greasy, an unpleasant odor develops and sometimes the coat begins to thin.

The whole problem may then receive the label “atopic dermatitis” and the dog is prescribed medication to reduce itching.

But there is one important question to ask: have we checked whether yeast is overgrowing on the skin or in the ears at the same time?

Apoquel can reduce itching very effectively, but it is not an antifungal medication. If Malassezia is overgrowing, that needs to be addressed separately. Modern guidelines for allergic skin disease also recommend looking for and treating secondary infections rather than assuming that all itching automatically comes from atopy.

What exactly is Malassezia?

The most important yeast in dogs is Malassezia pachydermatis. It is not usually an infection that the dog simply “picked up” from outside. Malassezia is part of the normal microbiota of healthy canine skin and mucous membranes. Its numbers can vary considerably between body sites, breeds and individual dogs, and routine sampling methods may not detect it at every normal skin site. So the question is not only whether Malassezia is present, but how much is present in a particular area and how that dog’s skin reacts to it.

A problem develops when the skin microenvironment changes in a way that allows the yeast to multiply excessively, or when the dog’s immune system reacts to it more strongly than usual. Malassezia dermatitis is often seen alongside allergic disease, adverse food reactions, keratinization disorders, hormonal conditions and skin folds.

So the most useful question is not simply “how do we kill the yeast?”

The more interesting question is: why was the dog’s skin able to keep the yeast under control before, and why can it no longer do so?

What does yeast overgrowth look like in dogs?

Typical areas include the paws and between the toes, ears, armpits, groin, neck, skin folds and the area around the mouth.

Signs that may point to yeast overgrowth include intense itching and licking, redness, greasy or flaky skin, brownish discoloration or discharge, a musty or rancid odor, hair loss and, in chronic cases, thickening and darkening of the skin.

These signs do not prove yeast overgrowth on their own. Bacterial infection, allergies, parasites and several other skin diseases can look very similar.

The simplest check: cytology

Diagnosing Malassezia usually does not require complicated laboratory testing. A veterinarian can sample the affected area using, for example, adhesive tape, a skin scraping or, in the ear, a cotton swab, and then examine the material under a microscope.

The World Association for Veterinary Dermatology considers cytology the main diagnostic tool for assessing Malassezia in everyday clinical practice.

This is particularly important in an itchy “allergic” dog.

If a dog receives only anti-itch treatment while the yeast remains untreated, the itching may improve for a while, but the whole problem has not been addressed.

Allergy and yeast can exist at the same time

This is where a false either-or way of thinking often appears.

A dog can have atopic dermatitis and Malassezia overgrowth. A dog can also have an adverse food reaction and yeast overgrowth at the same time.

Allergic inflammation changes the skin barrier and its microenvironment, which can in turn favor Malassezia overgrowth. The yeast can then further amplify inflammation and itching.

This is why guidelines for allergic skin disease recommend assessing secondary bacterial and yeast infections and treating them separately when necessary.

What about food?

In our view, food is an important part of the yeast discussion.

It used to be common to say that “yeast feeds on sugar and carbohydrates” and that the solution is simply to remove carbohydrates from the dog’s diet. In the case of cutaneous Malassezia, that is too simplistic an explanation.

But that does not mean food has no role.

A food component that does not suit a particular dog can cause or maintain an adverse food reaction and skin inflammation. Dogs with adverse food reactions very often itch on the paws, face, ears and underside of the body, which are exactly the areas where secondary yeast overgrowth is also common. The most reliable diagnostic method for an adverse food reaction is still a properly controlled elimination diet followed by a food challenge.

This is also where FendaF’s years of practical observation come in: we have seen dogs whose skin and ear problems clearly worsen after eating a food that does not suit them, and settle when a suitable diet is found.

That does not prove that a particular food “fed the yeast”. A more plausible pathway may be:

unsuitable food → inflammation or immune reaction → change in the skin microenvironment → better conditions for Malassezia growth

If the problem keeps recurring, diet deserves to be taken seriously.

How do you run a food trial so that it actually tells you something?

The least useful elimination diet is one where the main food is changed but the dog still receives ten different treats, chews, bites from another dog’s bowl, leftovers from the human table and flavored supplements.

If you genuinely want to know whether food affects the dog’s skin, the trial needs to be controlled.

We prefer a carefully selected novel-protein diet. A complete food with a simple ingredient list can also be a practical option if you know exactly which proteins the dog has eaten before.

The important thing is not whether the label says “raw”, “dry” or “wet”, but that there are as few changing variables as possible during the trial. If homemade or raw food is used for a longer period, it must be nutritionally balanced.

Can antibiotics affect yeast overgrowth?

This is an area where precision matters.

Veterinary dermatology consensus guidelines note that antibiotic treatment has not been demonstrated to be an independent risk factor for Malassezia dermatitis. At the same time, veterinarians do sometimes see yeast dermatitis or otitis develop relatively soon after an antibiotic course.

One biologically plausible explanation is microbial competition: an antibiotic changes bacterial populations and therefore the wider skin microecology. At present, however, that mechanism cannot be presented as a proven causal relationship.

So we would not write “antibiotics cause yeast”. But we also would not dismiss an owner’s observation if the same problem appears after every antibiotic course.

Repeated patterns like that are worth writing down.

Faddy’s experience after medication

Years ago, after treatment for leptospirosis and a fairly heavy medication load, Faddy developed intense redness and itching in his armpits. At the time we treated it as yeast overgrowth and I added apple cider vinegar to his food. Within a few weeks, the skin settled.

That is our experience, not a controlled study. We did not have cytology at the time to prove that Malassezia was the cause, and we cannot prove that apple cider vinegar was what produced the improvement.

But it is a good example of why the owner’s timeline can matter: what happened before the problem began?

How is Malassezia treated?

If cytology confirms Malassezia overgrowth, the most logical step is to reduce the yeast burden directly where the problem is occurring.

Mild or moderate skin disease is often treated topically. For severe, very widespread or poorly responsive disease, a veterinarian may use systemic antifungal medication.

The World Association for Veterinary Dermatology found the strongest clinical evidence for a shampoo containing 2% miconazole plus 2% chlorhexidine. A 3% chlorhexidine shampoo also has evidence from a controlled study.

But there is an important “but”.

Chlorhexidine can help, but it does not suit every skin

“Best studied” does not mean “best tolerated by every dog”.

In a randomized Malassezia study, a 3% chlorhexidine shampoo effectively reduced yeast counts, but adverse effects were reported in four of the 22 dogs during treatment.

In another randomized study, dogs with superficial pyoderma were treated with a protocol using 4% chlorhexidine shampoo and solution. Two of 31 dogs discontinued treatment because of adverse effects including redness, scaling and itching.

The 2025 ISCAID guideline also notes that topical antimicrobial products can cause redness and itching, usually soon after application, and that contact dermatitis can rarely develop after repeated use. If a reaction occurs, changing the formulation, active ingredient or concentration can be considered.

FendaF’s experience with chlorhexidine

Oscar developed very intense itching after being washed with a chlorhexidine-containing shampoo. I immediately washed him again with a different shampoo, and the intense itching stopped.

One of our clients’ dogs has also developed a similarly strong skin reaction after a chlorhexidine-containing shampoo.

These cases do not allow us to say whether the cause was chlorhexidine itself, another shampoo ingredient, or a combination of ingredients. But our experience is consistent with the fact that similar reactions have also been reported in controlled canine studies.

For that reason, we do not automatically recommend a chlorhexidine-containing shampoo for every dog with yeast overgrowth.

If a dog suddenly becomes much itchier after washing, the skin becomes redder or a rash develops, there is no reason to keep using the shampoo simply because the active ingredient is effective in scientific studies.

What if chlorhexidine does not suit the dog?

Chlorhexidine is not the only road to Rome.

For example, in a small study of a shampoo containing 2% climbazole, Malassezia counts decreased significantly after the first wash and the effect was still measurable after the second use. The study included only 11 dogs, so it does not provide an evidence base comparable with chlorhexidine, but it does show that alternative antifungal active ingredients exist.

A small randomized placebo-controlled study has also shown reduced Malassezia counts after use of a topical non-azole veterinary product on the paws.

In practice, depending on the affected area and the individual dog, a veterinarian may choose a product containing miconazole, ketoconazole, climbazole or another antifungal ingredient. It is worth looking at the whole formulation, not just one active ingredient.

What about thyme and other plants?

This is where things get interesting.

A 2019 study tested thyme oil, oregano oil, thymol and carvacrol against microbes isolated from dogs with otitis externa. All four showed laboratory activity against Malassezia pachydermatis as well.

Similar laboratory findings have been reported in later studies. That is also why I would not simply throw our old thyme article into the dustbin of history.

But two very different things need to be separated here.

The fact that thyme essential oil inhibits yeast in a laboratory does not prove that thyme sprinkled over a dog’s food treats Malassezia dermatitis.

A small amount of thyme can be added to a dog’s food as a culinary herb if the dog tolerates it. It may have a place in integrative nutrition, but I would not call it a treatment for yeast dermatitis.

I would be even more cautious with essential oils. There is a small clinical study of a specially formulated essential-oil blend in dogs with Malassezia otitis, but a controlled veterinary product is not the same as mixing an arbitrary essential oil with water at home. Essential oils must be diluted according to specific rules, and those rules need to be followed very carefully.

What about apple cider vinegar?

Apple cider vinegar is popular in integrative practice, particularly as a way of supporting an acidic skin environment, and we have also had positive experiences with it ourselves.

But I have no reason to present it as a clinically proven treatment for Malassezia.

More importantly, an acidic solution can sting intensely and may irritate inflamed, abraded or scratched-open skin.

If the dog reacts painfully or the skin becomes redder, “that means it is working” is not a good interpretation. Stop using it.

I would not recommend putting homemade acidic solutions or essential-oil mixtures into an ear until a veterinarian has examined the ear and the condition of the eardrum is known.

What can an owner actually do at home?

First, keep moisture-prone areas dry. Dry the paws thoroughly after wet walks, swimming and bathing, especially between the toes and in skin folds. Wash the dog’s bedding and keep affected areas clean.

Read more: Itchy Skin in Dogs: 10 Natural Remedies

If you use a topical antifungal product, watch the dog’s skin carefully after the first few applications. A sudden increase in itching is not something the dog simply has to endure.

If the problem keeps recurring, look at the whole picture: diet, allergies, ear health, the skin barrier, medication, moisture and possible hormonal disease.

And if the same problem always returns after treatment, the next question is not only “what should we use to knock the yeast down this time?”

The question is: why does it keep coming back?

When should you definitely see a veterinarian?

If the skin is wet, painful, bleeding or ulcerated, the dog is in severe pain, the ear has heavy discharge or a strong odor, the head is tilted, balance problems develop, or the problem does not respond to topical treatment within a short period, further diagnostics are needed.

It is also worth repeating cytology if treatment is not working. The fact that a dog had yeast overgrowth three months ago does not automatically mean today’s itching is yeast as well.

In summary

Malassezia is not an enemy that needs to be eradicated from the dog’s body forever. It is a normal skin inhabitant that can overgrow when conditions become favorable.

Good management therefore has two parts.

First, bring the yeast burden under control.

Then ask why the yeast began to overgrow in the first place.

For some dogs the underlying issue is allergic skin disease. For others it is an adverse food reaction. Some have moist skin folds or a chronic ear problem. Sometimes medication or an antibiotic course appears on the timeline. Often several factors are present at once.

Reducing itching can be very important for a dog’s welfare. But suppressing the itch and finding its cause are not the same thing.

That distinction is worth remembering whenever Malassezia becomes a recurring problem.

Sources

• Bond R, Morris DO, Guillot J, et al. (2020). Biology, diagnosis and treatment of Malassezia dermatitis in dogs and cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology.
• Miller J, Simpson A, Bloom P, et al. (2023). 2023 AAHA Management of Allergic Skin Diseases in Dogs and Cats Guidelines. 
• Udraite Vovk L, Mueller RS. (2026). Adverse Food Reactions in Dogs and Cats.
• Maynard L, Rème CA, Viaud S. (2011). Comparison of two shampoos for the treatment of canine Malassezia dermatitis: a randomised controlled trial. 
• Borio S, Colombo S, La Rosa G, et al. (2015). Effectiveness of a combined (4% chlorhexidine digluconate shampoo and solution) protocol in MRS and non-MRS canine superficial pyoderma: a randomized, blinded, antibiotic-controlled study.
• Loeffler A, Cain CL, Ferrer L, et al. (2025). Antimicrobial use guidelines for canine pyoderma by the International Society for Companion Animal Infectious Diseases (ISCAID). 
• Cavana P, Petit J-Y, Perrot S, et al. (2015). Efficacy of a 2% climbazole shampoo for reducing Malassezia population sizes on the skin of naturally infected dogs.
• Sjöström Y, Mellor P, Bergvall K. (2018). A novel non-azole topical treatment reduces Malassezia numbers and associated dermatitis: a short term prospective, randomized, blinded and placebo-controlled trial in naturally infected dogs. 
• Sim JXF, Khazandi M, Chan WY, et al. (2019). Antimicrobial activity of thyme oil, oregano oil, thymol and carvacrol against sensitive and resistant microbial isolates from dogs with otitis externa. 
• Gómez-García M, Madrigal I, Puente H, et al. (2022). In vitro activity of essential oils against microbial isolates from otitis externa cases in dogs.
• Nardoni S, Pistelli L, Baronti I, et al. (2017). Traditional Mediterranean plants: characterization and use of an essential oils mixture to treat Malassezia otitis externa in atopic dogs. 

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