Benadryl for Cats: Benefits, Safety, Dosage and More! Team


Medically reviewed by

Ivana Crnec. DVM

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Has your cat been sneezing, had watery eyes, and runny nose? Experienced a bee sting or bug bite and constantly itching? Or perhaps, developed an adverse vaccine reaction? If your cat was in any of these situations before, chances are the vet recommended Benadryl. 

The most popular antihistamine medication, Benadryl, although not FDA approved for use in veterinary medicine, is prescribed to allergic cats on a daily basis. This is because the drug is safe, efficient, and readily available. In this article, we will talk about Benadryl for cats.  

Can I Give My Cat Benadryl?

Can I Give My Cat Benadryl

Yes, you can give your cat Benadryl. However, first, you need to talk to your veterinarian. There are a number of factors affecting the safe use of Benadryl in cats, such as size, age, medical history, and concurrent use of medications. 

Benadryl is the brand name of the drug Diphenhydramine – a first-generation antihistamine medication. It is available over-the-counter and in veterinary medicine used off-label for allergy management in cats.  

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When to Use Benadryl for Cats

Same as in humans, Benadryl is used in our feline friends when suffering from allergies. But what is Benadryl for cats, and how does it work? 

As mentioned, the active ingredient in Benadryl, Diphenhydramine, is an antihistamine med, meaning it works by inhibiting the histamine effects in the body. Namely, when allergic reactions occur, the body produces histamine necessary for supporting the inflammatory and allergic processes. 

The released histamine travels through the body and binds with its specific receptors called H-receptors (located in small blood vessels and smooth muscles). Once histamine binds, it results in itchiness, swelling, and allergy symptoms. By blocking the histamine, Benadryl prevents the chain of reactions that lead to allergies. 

Benefits and Uses of Benadryl for Cats

Here are some of the proven and vet-approved uses of Benadryl for cats.

Benadryl for General Cat Allergy Issues. Cats are prone to various forms of allergies, but food and environmental are the most common. Cat allergies usually require multimodal management. However, Benadryl will treat the itchiness, inflammation, and other allergy symptoms. 

Benadryl for Acute Allergic Reactions in Cats. Common acute allergic reactions include insect bites and vaccine reactions. Both situations are potentially fatal if left untreated. Benadryl for cats is a good first-aid, but it is not the sole treatment – you still need to see a vet as soon as possible. 

Benadryl for Cat Motion Sickness. Because of its anti-nausea effect, Benadryl is be used in cats suffering from motion sickness during long car rides. Considering the fast and long-lasting nature, Diphenhydramine is an excellent choice when traveling with pets. 

Potential Side Effects and Risks of Benadryl for Cats

Potential Side Effects and Risks of Benadryl for Cats

Benadryl for cats is safe at the correct dosage, but it can have some side effects in an extra sensitive feline friend. Here are some of the more common side effects in cats:

  • Depression or hyperexcitability  
  • Dry mouth or foaming at the mouth
  • Vomiting and/or diarrhea 
  • Appetite loss 
  • Urine retention

Diphenhydramine, same as most antihistamine medications, must not be used in:

  • Cats allergic or sensitive to the active ingredient
  • Cats receiving meds with known drug interactions 
  • Extremely stressed and agitated cats
  • Pregnant and nursing females

On the other hand, Benadryl needs to be used with extra caution and under the vet’s close monitoring in:

  • Cats with heart disease and high blood pressure
  • Cats diagnosed with different forms of glaucoma

Finally, it should be noted that in case of acute allergic reactions (like, for example, snake bites or scorpion stings), Benadryl is just a first-aid – it is not the sole treatment, and you still need to seek prompt veterinary attention. 

Benadryl Dosage for Cats 

Benadryl is available in various forms – tablets, gel capsules, liquid, and spray. The gel capsules should be avoided for pets because they often contain potentially harmful ingredients. Perhaps the easiest way to give your cat Benadryl is to search for a compounding pharmacy and ask them to add a cat-friendly flavor/odor (for example, chicken).

The recommended dosage of Benadryl for cats is 1 milligram per pound of body weight. In more practical terms, the average 10-pound cat would need one-half of the regular 25 mg tablet or 4 ml of liquid Benadryl (the liquid form contains 12.5mg per 5ml). 

If you accidentally miss a Benadryl dose, you have two options – give it to your cat as soon as you remember or skip it completely and then continue with the scheduled dosing. Regardless of what you decide, do not double up the next dose as a compensation form. 

Giving your cat too much Benadryl can have severe consequences and may even result in an antihistamine overdose. A cat with such an overdose requires urgent veterinary help and is likely to exhibit the following signs and symptoms. 

  • Extreme sedation or hyperactivity 
  • Increased heart rate
  • Respiratory depression 
  • Tremors, seizures, and coma

Benadryl for Cats Usage Guidelines

Benadryl is a fast-acting medication with long-lasting effects. It kicks in within 30 minutes of administration and lasts for between 8 and 12 hours. This is useful when using Benadryl on an as-needed basis. 

Like all active ingredients, Diphenhydramine may interact with certain medications. The known Benadryl drug interactions include:

  • Anticholinergic drugs 
  • Epinephrine or adrenaline 
  • Tricyclic antidepressants (amitriptyline)
  • Monoamine oxidase inhibitors MAOIs (selegiline)
  • CNS depressants (sedatives, anesthetics, and pain meds)
  • Nitrofuran antibacterial agent (furazolidone)
  • Certain scabicides (amitraz)

If you prefer a natural alternative for managing your cat’s allergy, you should try CBD oil for cats. Cannabidiol prevents overreactions of the immune system and soothes common allergy symptoms. We recommend using the Honest Paws CBD products – CBD oil and CBD treats. They are made of full-spectrum and organic hemp and will boost your cat’s overall health and wellbeing. 

Our Final Thoughts on Benadryl for Cats

Potential Side Effects and Risks of Benadryl for Cats

Allergic cats can enjoy the benefits of Benadryl, an old-fashioned, first-generation antihistamine medication. In fact, allergies are only one thing that Benadryl helps with, the other one is motion sickness. 

However, before sneaking a Benadryl tablet in your cat’s favorite treat, do not forget to talk to your trusted veterinarian. Do not forget that the information in this article is to broaden your horizons and not a substitute for professional advice.