Benadryl for Severe Scratching in Cats

The correct dose of antihistamine can help stop that itching.
i Jupiterimages/ Images

Human allergies inflame the sinuses; in cats, they inflame the skin. Benadryl, or any regular-strength antihistamine whose sole active ingredient is diphenhydramine, often eases discomfort in cats. Get Kitty to the clinic if she's scratching obsessively to eliminate serious concerns, and ensure your vet advocates off-label antihistamine use.

How It Works

Benadryl is the household-name-brand drug released in 1946 and now available in generic form universally. In the United States, Benadryl and generics use the active ingredient diphenhydramine, typically in a hydrochloride base. The over-the-counter medication combats allergy symptoms, among them itching and inflammation. Diphenhydramine is an antihistamine, meaning that it deals specifically with histamines -- inflammatory biochemicals that cause skin redness, swelling, pain, increased heart rate and drop in blood pressure drop when perceived by receptors in the body. Benadryl blocks them from doing so, preventing symptoms.

Which Form to Buy for Cats

Benadryl comes in 25 milligram and 50 milligram capsules,12.5 milligram chewable tablets, 50 milligram tablets, an oral elixir and a syrup. For cats, one of the oral forms is recommended. It is easier to measure a precise dose with liquid than with pills. It is also very difficult to get cats to eat or swallow pills.

Dosage, Side Effects and Effectiveness

According to the Cat Health Guide, you can give your cat 2 milligrams per pound of body weight every 8 hours. For example, if your cat weighs 10 pounds, you would give him no more than 20 milligrams per dose. It works best if given to your cat before exposure to the cause of the itching, but if the cause is something in your cat's environment, this is obviously not possible. Drowsiness is a side effect of taking Benadryl for cats just as it is for humans. Another is a strong anti-nausea effect, which is not a bad thing. According to Mar Vista Vet, a California veterinary clinic, Benadryl is not as effective in animals as in humans. It may work within an hour of giving it, or a couple of weeks may elapse before relief is noted. Until then, it's liable to make your cat too drowsy to lick and scratch.


Do not give your cat Benadryl if he takes any form of tranquilizer. Also, do not give him just any Benadryl-brand medicine or even any antihistamine. Make certain that the antihistamine you give your kitty contains nothing but diphenhydramine as an active ingredient. Benadryl products that treat other symptoms such as headaches contain other active ingredients as well. Some such substances, such as acetaminophen, can be lethal to pets. Whether you use Benadryl or a generic, make sure it's regular-strength, no-extras diphenhydramine.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

the nest