My cat’s farts smell like death or rotten eggs. What is wrong?

Cats, just like all mammals, can experience flatulence. This is also known as farting. We may be startled hearing these noises coming from our little kitties, but occasional farting is a very normal digestive process. What is not normal is when farting becomes excessive, is very foul smelling, or is accompanied by other signs of gastrointestinal upset. In this article, we will review:
1) top causes of smelly farts in cats,
2) things you can do at home to help, and
3) when you should take your cat to the vet.

Why gas builds up in cats’ digestive system

Gas buildup in the digestive system is very common. It is a normal by-product of the breakdown of food and nutrients. This gas is produced by bacteria in the large intestine (or colon) when nutrients and foodstuffs are metabolized by the gut bacteria. A fart is heard when this gas is released through the anus, making a very characteristic tooting sound. See this article for more information on farting in cats.

Do cat farts usually smell bad?

Yes and no! Cats eat diets that are very rich in protein, leading to that pungent odor of their feces. Think about how strong-smelling cat poop is compared to a herbivore’s poo like a horse or cow. All poop is smelly, but animals that are carnivores have even stronger smelling feces secondary to the breakdown of these proteins. For this reason, cat farts may be smelly as well.

Most of the time, cat farts have a minimal smell and are very quiet. This makes it easy to miss if your cat is experiencing gas. Farts may have a variety of smells depending on your cat’s diet. Very foul-smelling and excessive farting is not normal.

Is it a sign that my cat is sick?

Excessive or very foul-smelling gas may be a sign of underlying illness. Occasional gas is very normal, but if farting becomes excessive, or your cat is displaying other signs of illness this may be a clue that something is wrong. A cat may normally fart one to two times a day, but the exact amount is unknown.

Why might my cat have smelly gas?

The list below are common causes of smelly farts:

  • Dietary related – Farting can be extremely common with diets that contain a large amount of fiber or carbohydrates. Fiber is broken down by gut bacteria that can subsequently produce excess gas. Carbohydrates are broken down into sugars and these can also lead to excess gas production by bacteria.
  • Protein-Rich Diets – Diets that are rich in protein are important for cats as they are true carnivores. High protein diets can lead to smellier gas, especially if they are formulated with fish protein.
  • Table foods – Human food can be very rich in fats or carbohydrates leading to excess gas. They can also cause an upset stomach which may lead to farting, diarrhea, or vomiting. A common misconception is that cats can have dairy products. After cats mature, they can no longer break down lactose. Feeding dairy items can lead to smelly farts, diarrhea, and bloating.
  • Gastrointestinal Upset – Tummy upset of any kind can lead to farting. Smelly farting may be the first sign that your cat is feeling unwell.
  • Gastrointestinal disease – IBD, gastrointestinal cancer, and malabsorption problems are all common causes of gas in cats. Diseases that cause poor absorption of nutrients can lead to excessive amounts of smelly farts. Cats with exocrine pancreatic insufficiency may have grey loose poops that are foul-smelling.
  • Parasites – Gastrointestinal parasites lead to poor absorption and digestion of food. This leads to gas buildup in the digestive tract and frequent farting. Tritrichomonas foetus and giardia are common causes of smelly farts and poop in cats.
  • Bacterial overgrowth – Overgrowth of bad bacteria in the gut can cause excessive bloating, smelly farting, and diarrhea. This is known as bacteria dysbiosis.
  • Food Intolerance/Allergies – Some cats can have sensitive stomachs and will not tolerate certain food types or ingredients. The first sign of this is typically farting or diarrhea.
  • Swallowing Air – Cats that eat quickly or have conditions that make them breathe fast (i.e. asthma) can swallow large amounts of air. This air will pass through the gastrointestinal tract and lead to farting.

What are other signs that my cat has gas?

Listed are the most common clinical signs in cats with gas:

  • Bloating
  • Increased gut sounds or borborygmi
  • Abdominal discomfort
  • Poor appetite
  • Decreased drinking
  • Behavioral changes: hiding, reluctance to play, resistance to petting their belly, or excessively cleaning their hind-end
  • Lethargy

9 things you can do at home to help your cat

If your cat develops gas, there are some simple remedies you can try at home:

  • Do nothing: Some cats will have short-lived episodes of smelly farts that do not require treatment. This is especially true if your cat is otherwise fine. This is appropriate for gas that doesn’t last more than one day. Your cat’s gas may just need time to resolve.
  • Consider a dietary change: If you just started a new diet, this could be a cause of farting. Always transition diets slowly. Give your cat a few days to see if their tummy works itself out, if not you may need to try a different diet.
  • Avoid diets that are high in carbohydrates or fats.
  • Avoid excessive fiber: Try to purchase foods that have fewer carbohydrates or fibers that can cause excessive bloating or farting.
  • Carefully select proteins: High-quality proteins should always be high on the ingredient list. Some protein sources like fish are high in fat and in general are smellier than poultry or beef. Try to avoid these diets if they don’t sit well with your cat.
  • Do not give table foods: Avoid cheese, milk, or rich items like bacon. Cats can no longer digest milk after they have become adults, so lactose can upset their stomachs.
  • Encourage your cat to eat more slowly: Eating quickly can cause the swallowing of large amounts of air. Consider a slow-down feeder or a treat ball.
  • Exercise: Appropriate amounts of daily exercise can help promote good gastrointestinal movement and function. Be sure your kitty is active and encourage extra play time, ideally after their meal has been digested.
  • Probiotics: Probiotics contain healthy bacteria that help to combat the overgrowth of bad bacteria. Probiotics can make stools and farts smell much better.

When should I take my cat to the vet?

Cat Has Intestinal Parasites

While farting can be normal, excessive smelly farting is not. This may be an early sign of gastrointestinal disease. Any cat who is farting and also has diarrhea or vomiting should be seen by a veterinarian. Bloating or poor appetite are also signs that something is amiss and should be investigated. Even in cats that appear healthy, too much farting should be brought to the attention of your vet.

What will a vet do?

A veterinarian has many options to investigate too much farting:

  • Abdominal palpation: Your vet will feel your cat’s belly thoroughly. This will help to characterize where the gas is coming from but also to see if there are abnormalities they can feel with their hands.
  • Check fecal sample: This is a great way to rule out gastrointestinal parasites as a potential cause of farting. Some vets may also consider prophylactic deworming, especially in high-risk kitties.
  • Bloodwork: Basic bloodwork may be performed to assess organ function and blood cell counts. Specific gastrointestinal panels can be performed to look for evidence of malabsorption, bacterial overgrowth, or digestive enzyme insufficiencies.
  • Imaging: If the above diagnostics do not give your veterinarian the answer they may recommend abdominal radiographs or an ultrasound to look for architectural changes in the abdomen.
  • Biopsies: A more invasive but sensitive test for gastrointestinal problems are biopsies of the intestinal tract. These are used to diagnose problems like IBD or cancers of the stomach/intestines. Biopsies can be performed endoscopically or surgically by a specialist.

FAQs

What ingredients give cats gas?

High amounts of fat, carbohydrates, and excessive amounts of fiber are the most common causes of gas in cats. Protein-rich diets are important, but anecdotally I’ve found that fish-based diets can cause gnarly smelling gas. Dietary intolerance can also cause excessive gas in kitties.

What should my cat’s poop look and smell like?

Normal cat poop comes in a variety of colors and consistencies. It can range from brown to light tan in color. It should always be formed in small nuggets or longer sausages with a smooth surface. The consistency of the stool should be firm but not too hard. Softer stools that lose shape may be a sign of gastrointestinal problems. Very hard, small stools may indicate dehydration or constipation.

As far as smell goes, cat poop is never pleasant due to cats being carnivores who eat a lot of protein. After living with your cat for a while, you will become accustomed to their natural odors. Extremely pungent or foul-smelling feces may be a sign that something is wrong.

Do cats fart out loud?

Most cats fart silently, but some cats will fart out loud. Most of the time we don’t hear the farts because kitties are such tiny creatures, but an occasional loud fart is not uncommon.

How can I tell if my cat has food intolerance?

Signs of food intolerance in kitties are excessive or foul-smelling gas, diarrhea, vomiting, poor appetite, weight loss, and bloating. You can troubleshoot food intolerance by gradually transitioning to a new diet with a novel protein source. Some examples of a novel protein are duck, rabbit, or venison. If your cat’s clinical signs improve, this may be a clear sign that they cannot tolerate certain proteins.

Read our other article on this topic:
Why is My Cat Farting A Lot?

Author

  • Dr Paula Simons, Veterinarian

    Dr Paula Simons graduated from the Ontario Veterinary College with a Doctorate in Veterinary Medicine (DVM) in 2019. She is currently working at 'Cornell University Veterinary Specialists' (CUVS) in Connecticut as an Emergency and Critical Care veterinarian resident (see her work profile). CUVS is a 24/7 Emergency and Critical Care Facility certified by the Veterinary Emergency & Critical Care Society, indicating the highest level of patient care.