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Dr. Geri Katz

When Your Cat Has Diarrhea… What Goes in Affects What Comes Out

This month’s mystery is about my own cat, Jimmy, who happened upon my driveway about two years ago.

The Problem

When I adopted him, he seemed very healthy except for one thing: he had diarrhea after every meal. I chalked this up to the fact that he had been an outdoor cat and had probably picked up a parasitic infection of some kind. I dewormed him, but saw no improvement. I submitted to the lab an extensive test looking for more unusual organisms but the test came back with no irregularities. I tried all kinds of anti-diarrheal medications but none of them worked.

The Diagnosis

After three months of chronic diarrhea, it dawned on me…maybe he has a food allergy? I fed him a meal consisting only of venison, something I was pretty sure he had never eaten before, and his stool was normal within 24 hours!  Why had I not thought of this before? Well, I had always thought that food allergies only affected indoor cats that were being fed processed food.  Boy, was I wrong, and so glad to have gotten to the bottom of this mystery!

About Food Allergies

Food allergies in cats are typically protein allergies.  They generally present in symptoms such as chronic vomiting, diarrhea or skin rashes in cats. There can be associated weight loss and poor hair coat. The usual proteins that are involved are beef, chicken, turkey, soy, or fish. There can be an allergy to one or more of these proteins.  Unfortunately, there is no accurate test to determine this, and even though there are laboratories that offer food allergy blood tests, they are thought to be inaccurate 50% of the time. The best way to know if your cat has a food allergy is to either feed them a novel protein they have never seen before, such as venison, rabbit, duck, or kangaroo, or to try feeding them a hydrolyzed diet, which is a prescription food where the digestion process has been mimicked by having the proteins, even ones the cat has seen before, broken down so that the molecules are small enough the body does not recognize them as foreign.

Beware of Cat Food Cross-Contamination

Beware, however, of running to the pet store to try a unique protein for your cat.  Unfortunately, the limited ingredient diets that are sold without a prescription are not made on dedicated machines.  This is akin to having a peanut allergy and eating a non-peanut item that was processed in a factory that also processes peanuts.  If the food doesn’t seem to help your cat, you won’t know if it is this means your cat does not have a food allergy or if there was just enough cross-contamination to make the test invalid.  The prescription diets are run through extremely rigorous testing to ensure that there is no contamination of any other protein in each batch of their foods and they are processed on dedicated machines.  I always advise my clients to start with the prescription food, and if it works, then they can try the over the counter food if they choose.

So if your cat has been having vomiting or diarrhea no matter what food you give them, or a skin rash that keeps coming back, there’s a good chance they have a food allergy!


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