Yeast – Yuck!

Yeast – Yuck!

I was prompted to write this article because someone showed me a photo of a very happy, white dog. At first, I thought that the dog was just dirty—maybe it had been having a ball playing in the mud, much to the dismay of its person. But when I looked closer, I recognized the telltale reddish-brown stains on its mouth, ears, feet, and around the eyes that can indicate an overgrowth of a species of yeast, Malassezia spp. This yeast just LOVES dogs!

We have all seen dogs that have reddish-brown tear stains under the eyes and around the mouth, and sometimes in other places like the groin area, between the toes, and at the base of the toenails where dogs have been licking. This staining can be caused by porphyrins that are secreted in tears and saliva. Porphyrins contain iron, which imbues the coat with a rust-colored stain. People often dismiss these stains, thinking they are just part of the way the dog is. In fact, they may not be normal at all.

It is important to determine why the dog is producing excessive tears and/or why it is licking the areas that are turning brown. The eyes might tear excessively for a variety of reasons, including blocked tear ducts or the conformation of the eyelids. One of the most common reasons for excessive licking of the feet and groin is allergies, so a visit to a veterinarian is in order to try to get the excessive tearing and/or licking under control. And while you are there, have your veterinarian check for that moisture-loving yeast.

People often dismiss these stains, thinking they are just part of the way the dog is. In fact, they may not be normal at all.

Good Yeast, Bad Yeast

Now I’m not talking about the yeast that was in such demand during COVID lockdowns, as people suddenly found the time to bake their favorite bread recipes. That’s good yeast. Malassezia is a bad yeast, at least when there is too much of it. True, it’s part of the normal flora—the organisms that typically inhabit the skin. Normally the body’s immune system keeps its growth in check. But when it grows out of control, it creates an imbalance in the body’s homeostasis—the healthy balance of your dog’s biological systems. The good news is that Malassezia overgrowth can be corrected.

Malassezia Overgrowth

There are two kinds of Malassezia overgrowth. Occasionally dogs will experience a massive overgrowth, in which large numbers of yeast grow on the skin and penetrate into the skin layers, causing hair loss, a darkening/reddening of the skin color, and the accumulation of greasy scabs. This type of infection can be seen in dogs that have endocrine disorders, immune suppression, allergies, or after long-term treatment with antibiotics or steroids, causing an imbalance of the normal bacteria that live on the skin and keep it healthy. That form of Malassezia overgrowth demands immediate veterinary attention, and often requires treatment with topical and/or systemic anti-fungal agents.

But let’s talk about the less extensive kind of Malassezia overgrowth that can cause milder, localized skin inflammation, ear and nail bed infections, and also causes unsightly brown stains around the eyes and on the mouth, ears, and feet. Besides the fact that those red-brown stains affect your dog’s appearance, it is important to reduce the amount of Malassezia growing on your dog because the fungus itself is quite immunogenic. It induces your dog’s body to mount an inflammatory response, which can induce a state of chronic inflammation on your dog’s skin. Chronic inflammation of any organ is undesirable, and the skin is actually the largest organ in the body. Reducing the number of Malassezia organisms growing on your dog’s skin and coat is key.

A Few of Yeast’s Favorite Things

What kind of environment favors the growth of Malassezia? This yeast would do very well on a tropical island, because it loves moisture and warmth. Your dog’s ears, facial folds (especially common in brachycephalic dogs), folds around the lips, skin between the toes, and other areas with skin folds, such as the vulva, are Home Sweet Home for Malassezia. As a result, the most important factor in reducing yeast growth is to keep these areas clean and dry. This can be done by wiping moist areas daily with an antimicrobial soap such as those containing chlorhexidine, followed by thorough drying. If your dog is a water baby, towel off their face, ears, and other susceptible locations when the water play is done.

To reduce the amount of yeast in your dog’s environment, make sure you put your dog’s food and water bowls in the dishwasher daily, using the sanitize setting. This will get rid of the biofilm that often covers these items and almost certainly contains yeast.

Of course, there are some areas that just cannot be kept clean and dry. This is particularly true for dogs that produce a lot of tears. Many small dogs have plugged or very small tear ducts, which can make them tear excessively. Brachycephalic dogs frequently have large eyes and small eyelids, which cause their tears to overflow. A visit to a veterinary ophthalmologist is always warranted, to be sure that there isn’t a physical reason for excessive tearing that could be corrected. Unfortunately, those chronically moist areas under the eyes can provide a perfect environmental niche for yeast growth.

What About Diet?

While there are no peer-reviewed data on the effect of diet on tear staining, my clinical experience suggests that non-allergic dogs that have tear staining can benefit from a change to a fresh diet. The images above show a client’s dog whose eyes were always stained, even though Chloe’s person cleaned them religiously every night. The top photo shows Chloe’s tear stains when she was fed kibble. The bottom photo was taken one month after Chloe was switched to a store-bought, fresh, frozen dog food. Nothing else was changed. Pretty amazing!

As you can see, with a little bit of home management, you might be able to significantly reduce or even abolish those awful brown stains, and even better, the yeast that causes them.