FACTS& MYTHS about YEAST DERMATITIS in DOGS:
A Board Certified Veterinary Dermatologist’s response to inaccurate internet information.
Karen Helton Rhodes, DVM, DACVD
Terri Bonenberger, DVM, DACVD
The above cartoon speaks volumes about many pet parents’ beliefs regarding yeast dermatitis in dogs. In this article, we try to counter some common andwell-circulated myths regarding Malassezia pachydermatis (yeast). We state 5 quick facts followed by 11 common internet myths/facts.
FACT: Dog’s harbor commensal (one organism benefits from the other without affecting it) yeast organisms on the surface of the skin. Malassezia pachydermatis (not M. pachydermatitis, as it is pronounced incorrectly in a popular YouTube video) can be found on normal dogs primarily around the nose, ears, mouth, anus, armpits, anal sacs, skin folds, nail/claw folds and interdigital regions. You can often see a red brown discoloration at the base of the nails with a yeast infection of the toes. Yeast love moist, dark crevices! Humidity is yeast’s friend. Seborrheic skin and allergic skin is prone to yeast overgrowth.
FACT: Yeast create a rancid, pungent, musty odor. Some people characterize the smell as corn chip or “frito-feet”.
FACT: Yeast organisms have a symbiotic (mutually beneficial) relationship with Staph bacteria on the skin. More bacteria on the skin = more yeast on the skin. Staphylococcus bacteria and Malassezia yeast produce mutually beneficial growth factors and alterations in their microenvironment. It is common for dogs with a yeast overgrowth to also have a bacterial infection. Yeast produce proteins and glycoproteins that allow the staph bacteria to adhere to skin cells. Keep in mind that the yeast organisms DO NOT INVADE the skin beyond the outer layer (stratum corneum). Yeast dermatitis results from an inflammatory or hypersensitivity reaction to yeast products and antigens.
FACT: Malassezia pachydermatis produces a number of inflammatory products that cause the skin to become moist, red, thickened with chronicity, and very very itchy! These products alter the skin’s pH and activate the inflammatory cascade in the skin that results in a hypersensentivity reaction. Chronic exposure to these products causes the skin to become thickened and lichenified (elephant skin). Constant scratching, licking or rubbing of the skin will also contribute to skin thickening….it is the “perfect storm”.
FACT: Intradermal Skin Testing for environmental allergies (trees, grasses, weeds, pollens, molds, dust mites, etc) can also identify an allergy to yeast!
_________________________________ MYTHS & FACTS________________________________
MYTH: Antibiotics will cause a yeast infection in your dog’s skin. Wrong
FACT: Antibiotic therapy has NOT been shown to cause an overgrowth of
yeast organisms. In fact, unlike Candida species (common cause of human yeast infections), Malassezia populations are not inhibited by bacteria. It is exactly the opposite: yeast numbers are enhanced when the skin is co-colonized with bacteria.
MYTH: Oral and/or topically applied Coconut oil will kill yeast or control yeast “outbreak”.
FACT: There is NO proof of any benefit from coconut oil applied topically or orally. It does not have antibacterial or antifungal properties that can be substantiated in any scientific study! It would also tend to make an already greasy dermatitis even more greasy! Not recommended topically yet likely not harmful orally.
MYTH: Brewers yeast in the diet will cause a yeast infection in the skin.
FACT: Brewer’s yeast will NOT influence Malassezia overgrowth. Brewer’s yeast is Saccharomyces cerevisiae and is considered a source of vitamin B, selenium, and chromium. There is one 2006 study in the human literature that showed patients demonstrated an INCREASE in salivary gland IgA levels after oral administration. Although this study is not in animals and is quite limited, it would appear to contradict the myth. It is doubtful that Brewer’s yeast would be either beneficial OR harmful for yeast dermatitis patients!
MYTH: “Most important aspect of addressing a yeast infection is through diet. Regardless of the cause, nutrition is the most important thing you should think about. Nutrition either supports (your dog’s) immune system to keep the yeast under control or it does the opposite and exacerbates a yeast overgrowth on the skin.” Dr. Karen Becker (general veterinary practitioner)
FACT: THIS IS NOT THE MOST IMPORTANT PART OF CONTROLLING YEAST. No scientific data to support her claims. False!
MYTH: Don’t use an oatmeal shampoo since the oatmeal will “feed the yeast”. Tea Tree oil or herbal shampoo recommended. Antifungal rinses or spray after a bath should be composed of vinegar, “essential oil mix”, lemon juice or even peppermint oil or lavender oil mixed with water.
FACT: Oatmeal shampoos will not perpetuate or “feed” Malassezia. First of all, the shampoo only has temporary contact (approx. 10 minutes). Second: carbs do not “feed” yeast organisms. On the other hand, an oatmeal shampoo, while not harmful, it is not especially beneficial. The above topicals are not recommended for use to control or even prevent yeast infections. You are better off using a shampoo or rinse with NaHypochlorite (not hypochlorous acid), miconazole, ketoconazole, or chlorhexidine: documented anti-yeast agents! These agents actually kill the yeast rather than just changing a pH or mechanically helping to remove them simply via a bath. Any bath is beneficial….thus the myriad of anecdotal reports!
MYTH: Carbohydrates or sugar in your dog’s diet will “feed” the yeast and cause infections! “Anti-Yeast Diets, Anti-inflammatory Diets, Species Appropriate Diets”. Sugar and Carbohydrates (honey, corn syrup, tapioca, grains) must be avoided in the diet since they will perpetuate or cause a yeast imbalance on the skin.
FACT: This is the biggest falsehood perpetuated by internet voices. Unfortunately, the loudest voice is a veterinarian. This statement has become viral among dog owners and these pet parents are adamant in their false belief.
Diet can be important when a food allergy (CARF: Cutaneous Adverse reaction to Food) is part of the underlying problem or etiology. If your dog is allergic to oats…then removal of oats from the diet will be beneficial. Likewise, if your dog is allergic to chicken ….removal of chicken is beneficial. Neither the oats nor the chicken directly caused the yeast overgrowth. The hypersensitivity reaction caused by the allergenic ingredient actually caused the organism imbalance.
Some people claim a direct link between yeast and carbs is due to the fact that carbs are converted to “sugar/glucose” in the body. Remember, the body will manufacture glucose regardless of the diet fed, even if all carbs are eliminated, in order to support life. Feeding more or less carbohydrate in the diet will not influence the growth of the Malassezia organisms on your skin…unless your dog is allergic to grains or carbohydrates…..and that is extremely RARE!
MYTH: Anti-fungal supplements that can be added to the diet are: garlic, thyme, oregano, parsley, raw apple cider vinegar, coconut oil, and fermented vegetables to reduce the level of yeast organisms on the skin. NO
FACT: Absolutely NO scientific data to support these claims. Anecdotal, at best. These additives are ingested and then they “magically” travel to the surface of the skin? I don’t think so! Remember, Malassezia does not penetrate past the upper layers of the skin!
MYTH: Witch Hazel in the ears to disinfect the ears and Hydrogen peroxide and tea Tree oil for the skin. NOT recommended.
FACT: Witch hazel is an astringent and irritating. Hydrogen peroxide is not an effective agent. Tea Tree oil can be toxic and it is also irritating. It function as an astringent. Anti-yeast properties are not documented.
MYTH: Apple Cider Vinegar will cure yeast infection. Antifungal rinses or spray after a bath should be composed of apple cider vinegar, “essential oil mix”, lemon juice or even peppermint oil or lavender oil mixed with water.
FACT: The only topical in this group with scientific data is the vinegar solution. It does not need to be apple cider vinegar. Vinegar: water @ a 1:10 dilution can be effective by changing the pH of the skin to an unfavorable environment for the yeast. Vinegar is acetic acid and lowers the pH.
MYTH: Supplements to re-establish normal yeast levels: probiotics, goldenseal, and caprylic acid….
FACT: NO supportive data but probably not be harmful.
MYTH: Immune testing for IgG, IgA, IgM will tell you if your dog is immunodeficient. These levels are low in a dog with chronic yeast infection. (This is incorrect and too simplistic)
FACT: 1st: These tests are not very accurate! 2nd and most importantly: Dog’s with Malassezia pachydermatis have elevated levels of serum IgA and IgG (immunoglobulins) over what is found in normal dogs BUT these antibodies do NOT appear to be protective in any manner. Cell-mediated immunity is likely more important than humoral (antibodies) immunity! You can see that the scientific data directly contradicts the myth. Rare cases of low IgA could have an increased incidence of yeast overgrowth due to immune dysfunction and the lack of control but research has shown that the defect in the control response is likely due to T-cell dysfunction rather than IgA (antibody). Immune testing is a waste of your $$ in most cases.
Interestingly, “immune compromised” dogs do NOT typically have a yeast dermatitis……..likely due to the fact that the immune response cannot over-react to the inflammatory proteases produced by the yeast organisms.
For more credible dermatology information to unleash your dog’s healthy skin visit www.HealthySkin4Dogs.com or Canine Skin Solutions, Inc. Facebook page.