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Lactose Intolerance in Cats: An Overview

Lactose Intolerance
Lactose Intolerance Guide:

Definition of Lactose Intolerance

While milk is not necessary to a cat's diet, it can be a treat if given from time to time. However, some pets cannot tolerate milk because they do not produce an enzyme called lactase. Lactase helps with the digestion of lactose, which is found in milk. After weaning, the level of lactase activity falls to about 10 per cent of its peak activity. In some animals, diarrhea will occur if more lactose (i.e. milk) is consumed than the pet can digest. This is called "lactose intolerance".

Lactose Intolerance, a common digestive disorder, is caused by the inability to break down the sugar in milk. That undigested sugar forms the perfect environment for bacteria to form in the intestinal tract and attack the stomach. cat and cat owners should be aware of the symptoms so they can remove all dairy products immediately from their pet’s diet if they think lactose intolerance is at work.

Causes of Lactose Intolerance

When adult cats eat milk or cheese, many of them will develop lactose intolerance symptoms such as gas, bloat, abdominal pain, and loose bowel movements. The reason that most cats experience these symptoms when they eat dairy products is that their digestive symptoms are not designed to handle these types of foods.

Cats are pure carnivores. This means that cats survive off of a diet of meat, tissue, and bone marrow. The digestive system of the cat does not easily digest rich foods such as milk and cheese products, and cats in nature never eat the lactose sugars in these products in the wild.

While kittens are able digest milk, this is due to the undeveloped digestive system of the young kitten. All mammals have digestive symptoms at a young age that are designed to digest their mother’s milk or a synthetic form of the milk. As mammals age, their digestive systems mature as well, and they are no longer able to properly digest rich dairy foods.

Symptoms of Lactose Intolerance

The most common and overt signs of lactose intolerance are vomiting and diarrhea, which isn’t surprising because the digestive system isn’t working properly. Sometimes a cat will drink excess amounts of water because lactose intolerance can also cause dehydration.

Since lactose intolerance is essentially an allergic reaction, owners should also look for the signs one might more often associate with allergies. For instance, if the cat or cat licks its paws or rubs its face on the floor, then its skin is clearly irritated and itchy, and this could be the result of lactose intolerance if dairy products are indeed a staple of the pet’s diet. It’s also possible that other allergic reactions like a mucus discharge from the eye or nose could occur, although this is less common.

Other dairy products can have a different effect. Cheese, for example, can cause constipation. This problem manifests itself in the cat and/or cat straining to have regular bowel movements and small, hard, and dry feces.

Even puppies and kittens, who can obviously tolerate their mother’s milk, are not necessarily immune to this problem. Puppies and kittens are often allergic to cow’s milk, but not their mother’s milk. This can lead to diarrhea and the pet being unable to wait until it’s outside to have a bowel movement. The best rule of thumb for a cat and/or cat owner is to severely limit or simply eliminate dairy products from their pet’s diet.

Some cats can handle the occasional bowl of milk with no problems, while other cats may have severe reactions to dairy products. The cause of this disparity is most likely due to slight genetic differences between cats.


Pets with milk intolerance can still consume dairy products under certain circumstances. For example, dairy products such as cheese (including cottage cheese) and unpasteurized yogurt usually have the lactose removed or have it partially broken down through bacterial action. As a result, these products are often well tolerated by cats that would otherwise get diarrhea after drinking milk.

It should be stated that neither boiling milk nor the use of skim milk affects an animal's ability to tolerate milk, since the lactose content remains unchanged in either case. The same applies to pasteurized yogurt and cultured milk (e.g. buttermilk), neither of which is well tolerated by lactase-deficient pets.

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