Can Yeast Really Make Your Cat Sick?


Yeast is a type of fungus that is commonly used in baking and brewing. It feeds on sugars and converts them into carbon dioxide and ethanol. While yeast is generally harmless to humans in small amounts, it can cause issues for cats if ingested in larger quantities.

When cats eat raw bread dough containing active yeast, the warm environment of their stomach allows the yeast to rapidly convert the dough’s sugars into ethanol (alcohol). This can lead to alcohol intoxication and other dangerous effects in cats. Even small ingestions should be treated as an emergency.

This article explores the sources of yeast exposure for cats, signs of yeast toxicity, proper diagnosis and treatment, prevention methods, and when veterinary care is recommended for cats that ingest yeast dough or other products containing live yeast cultures.

What is Yeast?

Yeasts are single-celled fungi, grouped in the biological kingdom Fungi. They belong to the phylum Ascomycota [1]. Yeasts were one of the first microbes studied by scientists. They are found naturally on plants, grains, fruits, and other surfaces. There are over 1,500 known species of yeast [2].

The most common yeast species used in food production are Saccharomyces cerevisiae and Saccharomyces boulardii. These yeasts convert sugar into alcohol and carbon dioxide during the fermentation process. This allows dough to rise in baking and produces alcohol in beer and wine making [3]. Some other places yeast is found is on the skin and mucous membranes of mammals.

Sources of Yeast Exposure for Cats

There are a couple main ways cats can be exposed to yeast in their everyday lives:


One source of yeast exposure for cats is through their food. Yeast is commonly found in many cat foods, especially cheaper brands that contain lots of carbohydrates, grains, or fillers. The yeast feeds on these ingredients and can proliferate in moist canned foods or bags of kibble once opened. Consuming excessive yeast from contaminated foods can allow it to overgrow in a cat’s body, leading to an infection (source).


Cats can also be exposed to yeast through their environment. Yeast is present on cat’s skin and can be transferred through grooming or contact with other pets. Overgrowth may occur if the cat’s immune system is compromised. Damp, moist environments like litter boxes, food bowls, and bedding are also breeding grounds for yeast. Keeping these areas clean and dry can help prevent exposure and infection (source).

Signs of a Yeast Infection in Cats

Some common signs of a yeast infection in cats include skin irritation and digestive issues. According to PetMD, yeast infections can cause greasy skin, hair loss, scaly skin, and itchiness [1]. Cats with yeast on their skin will often scratch, lick, and chew at the affected areas. Yeast infections in and around a cat’s ears may cause head shaking and scratching.

Digestive issues like diarrhea, vomiting, and loss of appetite can also indicate a yeast infection, especially if accompanied by skin irritation [2]. In severe cases, yeast infections in a cat’s mouth can cause drooling, lesions on the gums, and ulcerations on the tongue. If the infection spreads systemically, it can even cause lethargy and behavioral changes.

Some of the most common visible signs of a yeast infection include greasy fur, scabs, bald patches, head shaking, and irritated skin. Digestive upset like diarrhea and vomiting may also occur. Left untreated, yeast can become a serious health threat for cats.

Diagnosing Yeast Infections in Cats

Diagnosing a yeast infection in cats often begins with a veterinary exam. The veterinarian will look for common signs of a yeast overgrowth, including greasy skin, hair loss, scaly skin, and redness or irritation around the ears, nose, mouth, and anus.

The most definitive way to diagnose a yeast infection is through a skin scraping and microscopic examination. The vet will use a scalpel blade to gently scrape affected areas of the cat’s skin onto a glass slide. This sample is then looked at under a microscope to check for an abnormally high number of yeast organisms. Skin scrapings allow the vet to differentiate between yeast overgrowth and other skin issues like allergies or bacterial infections.

According to PetMD, “The diagnostic procedure for candidiasis can be carried out in a number of ways. In case of lesions, a biopsy to confirm or dismiss diseased tissue is imperative.”

Blood tests may also be used to check for elevated white blood cell counts, which can indicate an active infection. Culture tests can identify the specific type of yeast involved as well.

Treating Yeast Infections in Cats

There are several treatment options for yeast infections in cats:

Anti-fungal medications are commonly prescribed by veterinarians to treat yeast overgrowth. Drugs like fluconazole, itraconazole, and ketoconazole can help kill off excess yeast in a cat’s body. These are usually given orally and the course of treatment may last several weeks to ensure the infection is fully resolved (

Medicated shampoos may also be recommended, containing ingredients like miconazole, chlorhexidine, or ketoconazole. These can help remove yeast overgrowth on the skin when the infection causes skin issues (

Dietary changes are often an important part of treating yeast infections in cats. Feeding high protein, low carbohydrate diets can help prevent yeast overgrowth. Eliminating sugars, starches, and carbs from a cat’s diet removes the nutrients yeast needs to thrive (

Preventing Yeast Infections in Cats

There are several steps cat owners can take to help prevent yeast infections in their feline companions:

Probiotics can help promote healthy gut flora and prevent overgrowth of yeast. Adding probiotic supplements or yogurt to your cat’s diet may help prevent yeast infections (source).

Maintaining good hygiene is also important. Regularly cleaning your cat’s food bowls, bedding, and litter box can help minimize exposure to yeast. Gently wiping your cat’s ears, face folds, and other areas prone to yeast buildup can also be beneficial.

Checking for signs of allergies or skin irritation and treating any underlying conditions can help prevent yeast overgrowth. Keeping your cat’s immune system strong with good nutrition and minimal stress is also wise.

Avoiding prolonged antibiotic or steroid treatment when possible is also recommended, as these can disrupt the normal microbial balance. Always finish the full course of any prescribed antibiotics to prevent resistance.

While yeast infections in cats are usually treatable, prevention is ideal. By encouraging healthy digestion, hygiene, and immunity in your cat, you can help stop yeast overgrowth before it starts.

Dangers of Yeast for Cats

Yeast in large amounts, or unaddressed yeast infections, can pose serious dangers to a cat’s health. Here are some of the most important to be aware of:

Systemic Infection

If a yeast infection is left untreated, the yeast can spread beyond the original site and create a systemic infection throughout the body. This can be life-threatening, especially if the infection spreads to major organs. Systemic yeast infections require aggressive antifungal treatment.


Yeast produces alcohol as it grows, which can result in alcohol toxicity if yeast levels get too high in the body. Symptoms of alcohol toxicity include vomiting, diarrhea, lethargy, and lack of coordination. This requires immediate veterinary treatment to flush toxins out of the body and get yeast under control.

When to See a Vet

In most cases, mild yeast infections in cats can be treated at home under the guidance of a veterinarian. However, there are some instances when it is crucial to take your cat to the vet.

According to, you should take your cat to the vet if they have a severe yeast infection that is not responding to at-home treatment. Signs of a severe infection include widespread redness, hair loss, ulcerated or thickened skin, and excessive scratching. Your vet can provide stronger antifungal medications and run additional tests to identify any underlying conditions contributing to recurring infections.

You should also see the vet if your cat experiences frequent yeast infections, according to Recurring infections could indicate an immune deficiency disease or endocrine disorder, which requires veterinary diagnosis and care. Your vet can help get to the root cause of why your cat is susceptible to yeast overgrowth.

In summary, take your cat to the vet promptly if they have a severe case of a yeast infection or experience recurring infections. The vet can provide stronger treatment options and identify any underlying illnesses predisposing your cat to fungal infections.


Yeast infections are a concern for cats, but with proper awareness and action they can be prevented and treated. While yeast is a naturally occurring organism, when overgrown it can cause skin, ear, and other issues for cats. By understanding common sources of yeast exposure, being attentive to signs of infection, and promptly treating symptoms, cat owners can stay on top of potential yeast problems.

The key is to catch yeast infections early before they worsen and become more difficult to treat. With prescription antifungal medications from a vet, most yeast infections can be successfully cleared. Preventive care like wiping paws after going outside, keeping ears clean, and feeding high-quality diets is also important.

While yeast can make cats sick if ignored, with proactive care and veterinary treatment it does not have to pose an ongoing burden. Stay alert for yeast infection risks and symptoms, and be prepared to take action if needed. With vigilance and proper care, yeast can be managed and your cat can continue enjoying good health.

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