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Benadryl for Cats

By | Last Updated: 23rd February 2023

What is Benadryl (Diphenhydramine)

Benadryl is the brand name for an antihistamine consisting of diphenhydramine as the active ingredient. It is primarily prescribed to treat itching due to insect bites, bee stings or allergies, as well as for motion sickness, travel anxiety, coughing (congestion), and sneezing [4, 2, 6]. It may sometimes be prescribed to manage feline asthma.

Can you safely give a cat Benadryl

Although not approved by the FDA for use in cats [4], veterinarians may prescribe Benadryl in very low doses. But it is never recommended to administer Benadryl to your cat unless prescribed by a vet.

Quick Information

Benadryl for Cats

Generic Name: Diphenhydramine

Brand Name: Benadryl

Type: Antihistamine

Who can take it: Humans, cats, dogs

FDA Approved: Not for use in animals [1]

Availability: Over-the-counter [2]

Available forms: Tablets, capsules, suspension liquid, injection

How does Benadryl work in cats

When there is an allergic reaction, a chemical known as histamine is released, which travels through the body searching for histamine receptors to bind to and cause itchiness, swelling, and other allergic symptoms [6]. Diphenhydramine, being an antihistamine, blocks the effect of histamine, and hinders its ability to bind with the receptors, thus minimizing the extent to which allergic reactions can affect the body [4, 6].

Benadryl dosage: How much can you give to a cat

Follow the prescription in regard to the dosage and duration of the treatment. Varying according to the size, weight, and age of your cat, the usually prescribed dosage is:

Oral Tablets Oral Liquid Intramuscular Injection
0.25-0.50 mg/pound twice a day [6] 0.4ml/pound [8] as many times as prescribed by the vet 0.50-1 mg/pound twice a day [6]

The duration of the treatment depends on the condition being treated [6].

Note: People often consider giving their cat Benadryl to calm them down for a car ride, or for a grooming session, especially for cutting their nails. However, it can be extremely hazardous to use Benadryl without medical supervision as it can lead to a toxicity that can easily turn life-threatening for your pet.

What to do if you miss a dose

Try to administer the missed dose as soon as you remember. However, if it is already time for the next dose, you should skip the missed one entirely and continue with the regular dosing schedule. It is inadvisable to give two doses at once [2].

Side-effects in cats

Common side effects may include [2]:

  • Drowsiness and sedation
  • Hyper-excitement
  • Dry mouth
  • Urine retention
  • Diarrhea
  • Vomiting
  • Loss of appetite

The cat may drool or foam at the mouth when you give the medication; this is normal as Benadryl tastes quite bitter to them.

What happens in case of an overdose

A Benadryl overdose might lead to severe toxicity in a cat, resulting in seizures, troubled breathing, coma, and even death. Immediately get in touch with the vet or the ASPCA Animal Poison Control Center Helpline (1-888-426-4435).

There is a general misconception that Benadryl can be used to euthanize a cat, but it is not recommended as the suffering it would cause to the feline will make it a rather inhumane way to put down a pet.

Contraindications: When not to give

It is usually not given to cats suffering from [2, 6]:

  • Heart diseases
  • Hypertension (High blood pressure)
  • Hyperthyroidism
  • Bladder disorders
  • Glaucoma

The medication is usually not prescribed to pregnant and nursing cats.

Inform the vet about any medications your cat might be getting; Benadryl is known to interact with the following drugs [2]:

  • Epinephrine
  • Selegiline
  • Furazolidon
  • Warfarin sodium
  • Heparin calcium or sodium
  • Amitraz
  • Central Nervous System depressants

Fexofenadine (Allegra), cetrizine (Zyrtec), loratadine (Claritine), and dimenhydrinate (Dramamine) are often considered as alternatives to diphenhydramine; but it is recommended to check with the vet before going for any of those.


    1. Can Cats Take Benadryl? – Canna-Pet.com
    2. Benadryl for Dogs and Cats – PetMD.com
    3. Can You Give a Cat Benadryl? – PetMD.com
    4.  Diphenhydramine (Generic Benadryl) – 1800PetMeds.com
    5.  Benadryl for Severe Scratching in Cats – Pets.TheNest.com
    6.  Diphenhydramine (Benadryl®) for Dogs and Cats – PetPlace.com
    7.  How to Use Benadryl for Cat Allergies – Cuteness.com
    8. Diphenhydramine HCl (Benedryl©) Dosing Chart For Cats and Dogs – Falseriver.vet

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