Can I Give My Cat Benadryl?

Here's what to do instead ☝

cat with Benadryl

If you notice your cat is dealing with seasonal allergies (or you just want her to totally chill out on your next car ride), you may be tempted to give her some of that Benadryl sitting in your medicine cabinet.

But you should think twice before dosing her up on your own. While Benadryl is generally safe for use in cats to treat mild allergy symptoms or car sickness, you should only give it to your cat under the supervision of your veterinarian, since a Benadryl overdose in cats can be deadly.

The Dodo spoke with several veterinarians to find out whether or not you can give cats Benadryl — and to find out what you should really do instead.

What is Benadryl?

Benadryl is a common over-the-counter medication for humans that can reduce allergy and cold symptoms. (Less frequently, it can also be used to treat occasional insomnia and motion sickness.)

“Benadryl is the brand name for diphenhydramine hydrochloride, which is an antihistamine,” Dr. Megan Conrad, a veterinary consultant for Hello Ralphie, told The Dodo. “When a person's (or pet's) body detects the presence of something they're allergic to, substances called histamines are released. These can cause itching, swelling, rash and other allergic reactions. Benadryl and other antihistamines reduce or block the effects of these chemicals.”

So basically, Benadryl prevents the chemicals in your body that make you feel itchy from working properly.

“It competes with allergy-inducing histamine on receptor sites, in essence blocking histamine from binding,” Dr. Stacy Choczynski Johnson, a veterinarian for Pumpkin Pet Insurance, told The Dodo.

That’s why it can reduce a lot of common allergy symptoms in humans — from hives and itchiness, to watery eyes and a runny nose.

What does Benadryl do for cats?

Benadryl isn’t licensed for use in cats, but your veterinarian might still recommend Benadryl in certain cases. However, you should avoid giving Benadryl to your cat without your vet’s guidance, since giving it incorrectly can be deadly.

“It should be given at the direction of your veterinarian — never give an over-the-counter medication without your vet's instructions,” Dr. Conrad said.

Mild allergy symptoms

The most common use for Benadryl in cats is to treat mild allergy symptoms.

“The use of Benadryl in cats is primarily for itching and allergic reactions, such as to bug bites, medications or injections,” Dr. Conrad said.

Car sickness or sedation

Your vet might also give your cat Benadryl to treat car sickness or to sedate your cat, but in most cases, another prescription medication that’s more appropriate for your cat will be recommended.

“It’s sometimes used to prevent nausea from car sickness and to cause mild sedation (though your vet likely has better options for these issues),” Dr. Conrad said.

When not to use Benadryl for cats

There are some cases when Benadryl isn’t the best solution for cats, and can even be dangerous, which is why it’s super important that you bring your cat to the vet before giving her any.

Chronic or serious health issues

Don’t use Benadryl to treat symptoms due to chronic or serious underlying health issues. Your vet will likely prescribe more effective treatments in those cases.

“Benadryl should not be something that is given often and in an attempt to treat serious health conditions, such as asthma or flea allergic dermatitis,” Dr. Linda Simon, a veterinary surgeon and a veterinary consultant for FiveBarks, told The Dodo. “While it can be of some use in a small number of medical conditions, there are often more appropriate medicines available.”

“There are other oral antihistamines that your veterinarian may recommend that may be more effective for your cat,” Dr. Choczynski Johnson added. “In the case of chronic allergies, other approaches to therapy are recommended. I recommend immunotherapy in the form of injections or a liquid that is given under the tongue.”

Severe symptoms

If a cat’s allergy symptoms are super severe, your best bet is to forget about the Benadryl in your medicine cabinet and get your cat to the vet immediately.

“If a cat is suffering from anaphylactic shock, they may experience a sudden onset of signs such as facial swelling, hives and difficulty breathing,” Dr. Simon said. “Rather than relying on an antihistamine, owners need to bring their pet to the vet clinic immediately.”

“If your cat is having severe issues or respiratory distress, it would be best to take them to a vet right away,” Dr. Sara Ochoa, a small- and exotic-animal veterinarian in Texas and a veterinary consultant for, told The Dodo.

And even if your cat has mild allergy symptoms or is just a little itchy, you should still take your cat to the vet to see if there’s a better solution. “Owners should always seek a veterinary opinion first, as an antihistamine may not be the most appropriate treatment for their cat,” Dr. Simon said.

Pre-existing conditions

“If your cat has an underlying health condition, is pregnant or nursing, or regularly takes other medications and/or supplements, you must have a conversation with your vet first before giving your kitty Benadryl,” Dr. Conrad said. “It can interact with some medications as well as exacerbating certain health problems.”

Allergic to Benadryl

Cats can be allergic to Benadryl, which is yet another reason why you shouldn’t give it to your cat without your vet’s guidance.

“If your cat is allergic to Benadryl, they should not take this medication,” Dr. Ochoa said.

Dangers of Benadryl for cats

Some Benadryl preparations can be made with other ingredients that can be poisonous to cats, so be sure to check the label before purchasing a product. “Beware of diphenhydramine that is prepared in combination with other human medications,” Dr. Choczynski Johnson said. “Cold and flu preparations may be toxic to cats.”

Benadryl side effects for cats

There are some side effects of Benadryl for cats, including the following:

  • Lethargy
  • Dry mouth
  • Drooling
  • Diarrhea
  • Urinary retention
  • Vomiting
  • Loss of appetite
  • Excitability

Will Benadryl make my cat sleepy?

“One of the main side effects is drowsiness,” Dr. Ochoa said.

“Benadryl may cause sedation, which in some cases is desirable,” Dr. Choczynski Johnson added. “In some cases, Benadryl has the opposite effect and causes excitement.”

Benadryl shouldn’t be used to put your cat to sleep, though, as there are other medications better suited for that purpose. “I do not recommend using Benadryl as an impromptu sleep aid,” Dr. Choczynski Johnson said.

Benadryl dosage for cats

“A typical dosage used is 1 miligram per pound twice a day,” Dr. Ochoa said. However, you should absolutely check with your veterinarian before trying to use it on your own.

If your vet recommends Benadryl, you can purchase it in a liquid or tablet form, though liquid is usually the better option because it’s easier to give your cat an exact amount.

“Tablets can be split, or owners may wish to purchase the liquid form,” Dr. Simon said. “This is an especially good option for smaller cats who require more accurate dosing.”

Your vet might recommend more or less Benadryl for your cat (or none at all) than what’s typically recommended, so you should really make an appointment before giving your cat Benadryl.

“Always consult your veterinarian first before administering,” Dr. Conrad said.

Signs of Benadryl overdose in cats

If your cat takes too much Benadryl, she might show signs of overdose, which include the following:

  • Extreme lethargy and sedation
  • Agitation
  • Aggression
  • Increased heart rate
  • Trouble breathing
  • Seizures
  • Vomiting
  • Diarrhea

“It's possible for an overdose to cause death as well,” Dr. Conrad said. “If you know your cat has just eaten (or been given) a potentially toxic dose of Benadryl, call your vet.”

Benadryl overdose treatment for cats

The course of treatment for a Benadryl overdose that your vet chooses will depend on your cat’s symptoms, which will show up differently for every cat. But a lot of times, recovery is possible with hospitalization.

“It depends on the side effects that are seen,” Dr. Ochoa said.

Once you call your vet after noticing symptoms of a Benadryl overdose, they might advise you to induce vomiting to “limit the absorption of the medicine,” Dr. Simon said — however if you get to the vet within a few hours they can usually do it themselves. (And you should never try to induce vomiting without talking to a vet first.)

If your cat requires hospitalization, “many times just IV fluids and supportive care will help them quickly recover,” Dr Ochoa said.

“When managing a recent overdose of antihistamines, vomiting is induced and the medication is neutralized with activated charcoal,” Dr. Chocynski Johnson said. “Symptomatic and support therapy is provided to adjust for depression, hyperactivity, fast breathing and elevated heart rate.”

Activated charcoal can be used to try and bind with the Benadryl so less of it is absorbed in your cat’s system. Your cat might also be given IV fluids to prevent dehydration and electrolyte imbalances, and may be prescribed “medication to treat symptoms such as increased heart rate and blood pressure, seizures and other reactions to toxicity,” Dr. Conrad said.

The bottom line is that although Benadryl can be safe for your cat when given in proper doses, most of the time a better medication is available, so you should always consult with a veterinarian first.

We independently pick all the products we recommend because we love them and think you will too. If you buy a product from a link on our site, we may earn a commission.