Has your cat experienced a bee sting or bug bite that’s causing swelling and itching? Or perhaps your cat has developed an adverse vaccine reaction? Maybe you have a cat with chronic allergies that cause inflammation in the skin. 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 cats having allergic reactions on a daily basis. This is because the drug is generally safe, efficient, affordable, 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
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The short answer is that 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 your cat’s size, age, underlying health conditions, and concurrent use of medications. 

Benadryl is the brand name of the drug diphenhydramine, which is a first-generation antihistamine medication. First-generation antihistamines are those that not only treat allergy symptoms but also cross the blood-brain barrier and cause sleepiness. Benadryl is available over-the-counter in name-brand and generic forms, and it is used off-label for allergy management in cats.  

Dr. Rhiannon Koehler says, “Diphenhydramine was created in the 1940s and remains a very useful medication today. Our favorite use for diphenhydramine in cats is for acute allergic reactions, such as a vaccine reaction. If your veterinarian has recommended you try Benadryl for your cat, rest easy knowing that the medication is affordable and easily accessible. Always speak with your vet before using a new medication to make sure it’s a safe option for your pet!”

When to Use Benadryl for Cats

Similar to its use in humans, Benadryl is used in our feline friends when suffering from allergies. The main difference, however, is that Benadryl is mostly used in cats for allergic reactions, such as to a bug bite or vaccination, rather than chronic environmental allergies. In humans, Benadryl is commonly used for both reasons. 

As mentioned, the active ingredient in Benadryl is diphenhydramine, an antihistamine, that 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 some smooth muscles). Once histamine binds, it results in itchiness, swelling, and allergy symptoms. By blocking the histamine, Benadryl prevents the chain of reactions that cause the uncomfortable and sometimes life-threatening symptoms of an allergic reaction.. 

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 allergens are the most common causes of chronic allergies. Cat allergies usually require multimodal management. 

However, Benadryl is sometimes added to the treatment protocol to treat itchiness, inflammation, and other allergy symptoms. Benadryl is rarely effective for the management of chronic allergies on its own.

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. 

If your cat is having difficulty breathing, do not attempt to administer oral Benadryl to them. This is an emergency, and you should promptly take them to an emergency veterinary service. Your veterinarian will have injectable forms of diphenhydramine that are more rapidly effective and safer to administer in a cat that may have swelling in its mouth or throat. 

Benadryl for Cat Motion Sickness. Because of its anti-nausea effect, Benadryl can be used in cats suffering from motion sickness during long car rides. Considering that the medication is fast, affordable, available over-the-counter, and has acted for around 8 hours, diphenhydramine is an excellent first choice when traveling with pets. 

That being said, diphenhydramine will not be enough to prevent motion sickness in most cats prone to getting sick on car rides. If Benadryl is not effective for your cat, your veterinarian has prescription medications available that are typically more effective.

Potential Side Effects and Risks of Benadryl for Cats

Potential Side Effects and Risks of Benadryl for Cats

Benadryl is safe for most cats 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
  • Constipation
  • Vomiting and/or diarrhea 
  • Appetite loss 
  • Urine retention

Diphenhydramine, the 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, hyperthyroidism, and/or high blood pressure
  • Cats diagnosed with specific forms of glaucoma
  • Cats with seizure disorders

Always consult with your veterinarian before giving any medication, even an over-the-counter medication such as diphenhydramine. 

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 safest way to give your cat Benadryl is to search for a veterinary compounding pharmacy and ask them to add a cat-friendly flavor/odor, such as 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 over-the-counter liquid Benadryl (the liquid form contains 12.5mg per 5ml).

If you purchase liquid or children’s Benadryl, ensure that diphenhydramine is the only active ingredient and that the product does not contain xylitol. Medications purchased from a compounding pharmacy may have a different concentration, so you should speak with your veterinarian to get appropriate dosing instructions.

According to Dr. Rhiannon Koehler, “Tablets and capsules can be very difficult to give to your cat. Consider using liquid Benadryl to make the administration of the medication a little easier. You can even get this medication compounded with other flavors to hopefully make administering the medication a little more tolerable for you and your feline friend.”

If you accidentally miss a Benadryl dose, you have two options: 1. Give it to your cat as soon as you remember, or 2. Skip it completely and then continue with the scheduled dosing. Regardless of what you decide, do not double up on the next dose. 

Giving your cat too much Benadryl can have severe consequences and may result in an antihistamine overdose. A cat with 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: Additional Usage Guidelines

Benadryl is a fast-acting medication with long-lasting effects. It kicks in within 30 minutes of administration and lasts 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 (atropine) 
  • Epinephrine or adrenaline 
  • Tricyclic antidepressants (amitriptyline)
  • Monoamine oxidase inhibitors (selegiline)
  • Central nervous system depressants (sedatives, anesthetics, and pain meds)
  • Nitrofuran antibacterial agent (furazolidone)
  • Certain antiparasitic medications (amitraz)
  • Potassium supplements
  • Prokinetic medications (cisapride, metoclopramide)

This list is not all-inclusive, and you should always discuss any medications your cat takes with their veterinarian before starting another medication. 

If you prefer a natural alternative for managing your cat’s chronic allergies, you could consider CBD oil for cats. Cannabidiol prevents an overreaction of the immune system and may soothe common allergy symptoms. 

We recommend using the Honest Paws CBD products – CBD oil and CBD treats. They are made of full-spectrum, organic hemp and will boost your cat’s overall health and well-being. Please note that CBD should not be used as a first-line treatment for acute allergic reactions, which require veterinary attention.

Our Final Thoughts on Benadryl for Cats

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Allergic cats can enjoy the benefits of Benadryl, an old-fashioned, first-generation antihistamine medication. However, before sneaking a Benadryl tablet into your cat’s favorite treat, do not forget to talk to your trusted veterinarian. The information in this article is meant to provide you with more information but is not a substitute for professional advice.