Can You Give Cats Benadryl?

Sandra C. Mitchell, DVM, DABVP
By Sandra C. Mitchell, DVM, DABVP on Sep. 28, 2022
Can You Give Cats Benadryl?

Perhaps at some point, your veterinarian has recommended Benadryl for one of your pets. Or maybe you have heard of someone using it for their cat, and you’re wondering if you can safely give it to your kitty to make her a little sleepy before her next vet trip.

Benadryl is a name-brand medication whose primary active ingredient is diphenhydramine, an antihistamine. Although it is not specifically labeled for use in pets, it is commonly recommended and used by veterinarians “off label.”

Here’s what you need to know about giving cats Benadryl.

Can You Give a Cat Benadryl?

For a healthy young cat, diphenhydramine is considered safe to use but should only be given under the direction of your veterinarian. It should not be administered without specific diagnostic and dosing advice.

Cats that should not be given diphenhydramine include:

In most cases, severe disease (such as anaphylaxis—severe allergic reaction) should not be treated at home with diphenhydramine without immediately seeing the vet.

Even milder signs, such as itching or sneezing, should be diagnosed before diphenhydramine is administered. Giving this medication can mask symptoms that are helpful to your veterinarian in making an accurate diagnosis.

Why Do Vets Sometimes Give Cats Benadryl?

The antihistamine diphenhydramine is used to treat acute allergic reactions (such as bee stings), for which it is very effective. Sometimes, however, it is also prescribed for chronic allergies, although it does not work well in all cats, and some trial and error might be needed to find which antihistamine works best for your cat.

It can also be used to help reduce the severity of motion sickness or to provide minor sedation. Benadryl can help some cats who are vomiting as well.

Although we do consider diphenhydramine safe to use for cats, there are a number of possible side effects:

  • Sedation (which can be pronounced)
  • Excitement (some cats have the opposite of the expected sedation, with significant excitement as a side effect)
  • Lethargy
  • Vomiting
  • Diarrhea
  • Dry mouth
  • Lack of appetite
  • Urine retention

Because of the significant number of side effects seen with diphenhydramine, in most cases, it is appropriate only on a short-term basis. Keep in mind that your veterinarian may have different recommendations for your pet’s individual situation.

Dosage for Benadryl in Cats

Most veterinarians will dose diphenhydramine using a combination of recommended doses and practical experience, since it is not labeled for use in cats. The VIN Veterinary Drug Handbook lists doses ranging from 1–4 mg per kilogram body weight.

It can be given orally or as an injection in veterinary hospitals. Quite a few oral formulations are available, so you need to consult with your veterinarian if you are considering Benadryl for your cat. Many over-the-counter options made for people have additional medications added or are extended-release formulas, both of which should be avoided.

The human liquid formulas can have a taste that is very objectionable to cats, and for many cats, the “standard” 25 mg capsules are too large. For these reasons, many pet parents choose to use either 12.5 mg capsules or scored 25 mg tablets for accurate dosing in cats.

Tablets that are not scored should never be split or broken for administration, as the medication may not be evenly distributed, and an accidental over- or under-dosing can occur.

Is Benadryl the Best Medication for Cat Allergies?

Although diphenhydramine is sometimes used to treat chronic environmental allergies in cats, antihistamine use in cats can be very hit or miss. While some patients will see a reduction in allergies when diphenhydramine is used, most do not.

And yet, if a kitty doesn’t respond to one antihistamine (such as diphenhydramine), they may respond to a different one. So it’s often necessary to try a number of different medications to find one that works.

In general, antihistamines are not a first-line treatment for cats with environmental allergies, and they are never used to treat other allergies, such as food allergies. It is important to have your cat tested, determine what they are allergic to, and then have your vet tailor the right treatment.

Flea allergies, for example, are best treated with appropriate flea control, while food allergies are treated with diet trials. Skin allergies in cats may be treated with allergy injections, steroids, or immune-mediating medications. Respiratory allergies (with symptoms such as runny nose and eyes as well as sneezing) are actually very rare in cats. Most cats with these signs actually have a respiratory infection and are not generally treated with antihistamines. So don’t assume your cat has allergies if you see these signs or try to treat them at home with human allergy medications.

If your veterinarian is recommending diphenhydramine, it’s most likely to treat an allergic reaction to something like a bee sting or to help combat motion sickness.

Photo Credit: iStock/freemixer

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Sandra C. Mitchell, DVM, DABVP


Sandra C. Mitchell, DVM, DABVP


Sandra Mitchell is a 1995 graduate of the New York State College of Veterinary Medicine. Since graduation, she has worked in many fields...

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