Analysis by Dr. Karen Shaw Becker
Yeast infections in dogs are fairly common, but unless you've had experience with a yeasty pet, you might not identify the problem right off the bat. In fact, many pet parents just assume their furry family member has a perpetual "stinky dog smell," when in reality, the problem is an overgrowth of yeast.
Yeast infections of the skin and ears in dogs are commonly caused by an organism called Malassezia pachydermatis. There are 18 species of Malassezia yeasts that exist as commensal (naturally occurring) organisms on mammalian skin. M pachydermatis is a "lipid-dependent" yeast that can become pathogenic, existing in excessive quantities on susceptible hosts and making them miserable.
A yeast infection can occur anywhere on a dog's skin, including between the toes, in the armpits, and in deep skin wrinkles and folds. But the most common location is the ears. Yeast love damp, warm environments and thrive when the immune system becomes unbalanced.
Dogs with a balanced immune system have healthy levels of yeast that occur naturally on the body, including on the paws. However, dogs with an unbalanced immune system are at risk of yeast overgrowth. Animals with weakened immune systems or those who are immuno-suppressed can end up with an overgrowth of yeast, as can dogs with overactive immune systems that result in allergies.
Malassezia research shows the fungus also affects how the immune system responds. In some circumstances, the fungus activates a massive cellular and humoral immune response, provoking an immune system over-reaction, and in some cases, there's an immunosuppressive effect.1
Yeast infections often occur during or after antibiotic therapy because these drugs reduce the beneficial bacterial levels necessary to maintain healthy skin defenses. Other factors that predispose dogs to yeast infections are increased humidity, altered skin pH levels (which is why I don't' recommend oatmeal shampoos) and prolonged corticosteroid therapy. 2
Yeast can be a problem for pets who are immunosuppressed, which includes those with an immunoglobulin deficiency or Cushing's disease, and those taking prescription catabolic steroids (e.g., prednisone).
Yeast overgrowth can also be a problem for dogs with a genetic predisposition to atopic dermatitis. Yeast infections are also indirectly associated with allergies, which are the result of an immune system overreaction. In fact, many dogs can be allergic to their own yeast.3
Allergies trigger a systemic inflammatory cascade that creates intense itching, which can lead to secondary bacterial skin infections, typically treated with antibiotics. The more antibiotics a dog is given, the worse the yeast infection tends to be.4 Along with antibiotics and corticosteroids, chemotherapeutic agents can also lead to yeast infections.
Dog breeds that may be at increased risk for yeast infections include Shih Tzus, West Highland White Terriers, American Cocker Spaniels, Basset Hounds, English Setters, Boxers, Poodles, Dachshunds and Australian Silky Terriers.5
A dog with a yeast infection feels uncomfortable, and the discomfort can range from mild to miserable. Almost all dogs with an overgrowth of yeast are excessively, persistently itchy at the site of the infection.
If it's a problem with your dog's paws or ears, for example, she won't be able to leave them alone. Chronic butt scooting can also be a clue. The terrible itchy feeling leads to desperate scratching and chewing, which can result in significant self-induced trauma and pain.
Another thing most pet parents notice is the smell. Yeast has a very distinctive odor, which has been described as similar to moldy bread, cheese popcorn, or corn chips. In fact, some people refer to a yeast infection on a dog's paws as Frito Feet. It's a pungent, musty, unpleasant smell that at times can be overpowering.
Many dogs have had a yeast problem for so long their humans don't realize their pet is stinky. I've had dog parents say, "I thought she was supposed to smell like that," because they've grown accustomed to the odor of their dog's chronic yeast problem.
Other signs of a yeast infection include areas of skin irritation, redness, and inflammation, especially in and around the ears, the toes and pads of the feet, the nasal, facial or other skin folds, the anus, armpits, neck, and sometimes around the tail base. There might also be scaly or oily skin, a greasy hair coat and/or hair loss.
Sometimes in chronic, severe yeast infections there are raised scaly patches of skin, or darkened, thickened skin. There might also be a secondary bacterial infection or a foul-smelling yellow-green discharge from the ears. There can also be behavior changes caused by the itching and pain, including depression, loss of appetite, anxiety, and even aggression.
Definitive diagnosis of a yeast infection requires either cytology (looking at a skin swab under a microscope) or culturing (submitting a sterile swab of the skin to the lab where the cells are grown and identified on a petri dish). Most veterinarians prefer skin cytology to identify yeast overgrowth in dogs.
If there's an ear infection, either diagnosed or suspected, it's extremely important to know whether the eardrums are still intact before putting any liquids, gels, cleansers, or other medications down in the ears. If one or both eardrums have ruptured, putting products into the ear canals can damage the middle and inner ear.
Most dogs with a yeast infection have it in more than one spot. For example, they can have it on all four paws, both ears, and in some cases, over their entire body.
In my experience, the most important aspect of addressing any chronic yeast infection, regardless of its cause, involves changes to the diet. Even the research suggests, "treatment of Malassezia is accompanied by other recommendations, such as a dietary elimination trial."6 The nutrition your dog receives either supports his immune system to keep yeast growth under control, or it does the opposite and exacerbates a yeast overgrowth situation.
Dogs with yeast need an "anti-yeast diet" that is anti-inflammatory and species-specific. I prefer to use a novel protein (a protein you haven't fed before), low/no starch diet for 3 months.
Dr. Anna Hielm-Bjorkman and her team found dogs with atopic dermatitis fed heat-processed high carbohydrate kibble or a raw meat-based diet had very different expressions of skin inflammatory markers. Raw food activated the skin's immune defense system, increasing antioxidant expression and having anti-inflammatory effects.7
I also recommend adding a few natural antifungal foods to the diet, for example, small amounts of fresh garlic,8 thyme, parsley, and oregano to help reduce the level of yeast naturally.9 Adding fermented veggies to your dog's meals can also be very beneficial, along with caprylic acid (found in coconut oil), which has anti-Malassezia properties.10
There are specific supplements your integrative veterinarian may recommend that will help re-establish normal healthy levels of yeast in your dog's body. Probiotics can be very beneficial, as well as the herbs pau d'arco or berberine (the active component in goldenseal, barberry and Oregon grape root). A 2016 study found berberine kills yeast directly but can also be used with anti-fungal drugs to enhance their effects.11
The more potent undecylenic acid, which is an organic unsaturated fatty acid can be beneficial in treating stubborn infections because it helps break down the yeast's biofilm. Olive leaf extract contains oleuropein, a potent antifungal natural extract that can also help.12
Unfortunately, some dogs suffer with year-round yeast problems no matter what food they're eating or remedies their owners are using to manage their condition. These cases can be complicated by demodex mange, and the root cause for both skin issues can be an immune system problem.
Long standing cases of chronic yeast infections in dogs aren't normal. In these cases, I recommend blood tests to measure immunoglobulin levels (IgG, IgM, and IgA), which are generally low with immunodeficient dogs (and high with allergic dogs). Addressing immune imbalances (both underactive and overactive responses) is an important piece of resolving chronic skin microbiome imbalances.
For skin yeast infections in dogs, I recommend a natural antifungal shampoo. I typically use a tea tree oil shampoo, as research shows it's helpful in reducing Malassezia on the body13 (never use an essential oil on your dog without it being diluted first).
You can bathe your dog as often as necessary, but once a week at a minimum. I don't recommend using oatmeal-based shampoos for pets with allergies or yeast infections because they don't do anything to assist in re-establishing a healthy skin microbiome.
I've seen excellent results in yeasty dogs with dietary adjustments and two to three baths a week, along with ear cleaning and foot soaks as necessary. Bathing your dog isn't always an easy or convenient task, but it's an inexpensive, safe, drug-free and effective way to control yeast and keep him comfortable.
I also recommend antifungal rinses and sprays in between disinfecting baths, and if you pour an antifungal rinse over your dog after a bath, it can help extend the number of days in between baths.
There are several different rinses you can try. I've had success with vinegar, lemon juice, and essential oils. Vinegar and lemon are astringents to Malassezia,14 so they're naturally drying and help with greasy or oily coats. Add one cup of vinegar or one cup of lemon juice — or 30 drops of lemongrass essential oil15 — to a gallon of water. Since lemon juice can lighten fur, I usually recommend vinegar or the essential oil mixes for dogs with dark coats.
After shampooing your dog and rinsing thoroughly, follow up with the gallon of natural antifungal rinse to knock down the amount of yeast remaining on the skin. Pour the rinse solution over your dog's body from her neck (not her head) to the base of her tail.
Rub the solution into her coat and skin, focusing on the areas where she is yeasty. Don't rinse the solution off, just pour it on, rub it in, and then towel dry. I've found lime sulfur dips can also be beneficial for resistant yeast infections.16
It's important to remember these recommendations won't produce results overnight. It takes time using any all-natural protocol to see improvement. If these easy, inexpensive solutions are effective at managing your dog's yeast issues, I'd recommend you continue the starch-free, anti-inflammatory fresh food diet year-round to minimize your pet's likelihood of recurring infections.