Benadryl for Cats: How Much Should You Give & How?

Updated on:
Some articles include affiliate links, and we may receive compensation when you make a purchase through these links.
benadryl for cats

Can the answer to your cat's problem be as close by as your medicine cabinet? If your cat sneezes, coughs and wheezes more than what would be normal or always seems itchy you might have wondered if it would be safe to give her a little dose of Benadryl.

Can cats take Benadryl? Generally, you are advised to provide your cat only medicine formulated for cats. However, in some cases a dose of Benadryl for cats is acceptable, if you're smart about it.

What is Benadryl?

Benadryl is a brand name for an antihistamine medication manufactured by Johnson & Johnson. Johnson & Johnson bills itself as “A family company”. Does this apply to pets as family members? It is not recommended for children under six. The Benadryl used as a topical solution is not to be consumed under any circumstances.

We can take this to mean that topical Benadryl should not be used on a cat as Kitty may swallow some while grooming. Would a small dose of orally administrated Benadryl be acceptable? More on that later.

What it Does and How it Works

Benadryl for Cats: How Much Should You Give & How? 1

When an inflammatory substance, known as histamine, locks onto a living cell this can cause irritation leading to an allergic reaction. The motor neurons of the nervous system release a chemical known as acetylcholine to activate muscles. This could result in either paralytic or convulsive seizures.

Benadryl for Cats: How Much Should You Give & How? 2

An antihistamine like Benadryl prevents the histamines from connecting with the H-1 receptors located on the small blood vessels and smooth muscles in the recipient's body. It blocks the transmission of acetylcholine as well. In this way, an allergic reaction is successfully avoided. Swelling goes down, eyes stop watering and the nose stops running. Itching stops and breathing becomes easier.

The active ingredient in Benadryl is diphenhydramine. The generic version of this drug, diphenhydramine hydrochloride, has the same effects and can be purchased at any drug store.

Benadryl for Cats? 

image of a kitty

Can cats take Benadryl? Only with extreme caution can you have your kitty take Benadryl. Many veterinarians agree that Benadryl, if administered properly, is reasonably safe to give to both dogs and cats.

Cat breeds prone to breathing problems to start with (such as Persians) may particularly find fast and effective relief with Benadryl.

However, there are many important factors to consider. How old is your cat? How big is your cat? Does your cat take other medications or have other medical problems?


If you suffer allergies, whether contact dermatitis or marked by sneezing or itchy eyes you may have been advised to take Benadryl. Many ailments suffered by humans are common in cats as well.

1. Cat allergies

Perhaps you let Kitty try new food, only to find out she's allergic. Allergies can develop spontaneously as well. If your new perfume, houseplant, deodorizer or household cleaner not only makes Kitty gag but have a full out attack where she can't breathe it might be something she's allergic too.

In some cases, taking the trigger away and letting Kitty breathe clean air might be enough. But, it could take her awhile to get back to normal, depending on the severity of the allergy.

2. Skin allergies

Some cats have sensitive skin. Maybe the detergent you used on her bedding or the shampoo you used on her contained something that makes your cat break out in a rash or hives. Plastic bowls, woolen bedding or toys made with latex may trigger a contact allergy in your cat.

If your cat has redness, inflammation or unexplainable bumps on her skin or just can't seem to stop scratching herself, she may be suffering from a skin based allergy.

3. Reactions to vaccines

image of a cat receiving a vaccine

Many cats are apt to have allergic reactions to vaccinations and new medications as well. It is of utmost importance that you monitor your cat after any shots or introducing her to unfamiliar medication.

Some vets may even insist that you and the cat stick around for a few minutes for observation after Kitty gets her shots. She may be given Benadryl before the shot is given just as a precaution.

Even if your cat never has experienced an allergic reaction to particular vaccines she may have an unexpected adverse response. Often these allergic reactions might become so severe that Benadryl by itself will not be enough.

4. Bug bites

Mosquitoes are more likely to go for the least hairy parts on a cat's body, which would be the nose, ears and stomach. And wouldn't you know it? These are the body parts that are the most sensitive!

If Kitty has a flea infestation, they'll bite anywhere. Fleas can make any cat itchy and uncomfortable, but some cats are unfortunate enough to be highly allergic to flea bites.

Some cats can get curious about flying, buzzing things and get themselves stung. What happens if Kitty is allergic to bee stings or wasp or scorpion venom? Even non-venomous snakes and reptiles may have bacteria in their mouths that can make a bite dangerous.

5. Cat cold

If the cold is due to a bacterial or viral infection antibiotic treatment may be required. All Benadryl will do in this case is reduce the symptoms. It must also be pointed out that Benadryl does not “cure” an allergy so much as inhibit the reaction.

6. Mild Sedative

image of a sedated kitty

If Kitty is going to be confined to a crate or other small space for an appreciable length of time (generally in cases of transportation) you may want to give her a little something to help her sleep through the whole thing. If Kitty is asleep, she will not be stressed out about being confined.

A little Benadryl may be the thing to help her calm down and just snooze through the whole ordeal. This is not recommended for elderly cats.

7. Anti-nausea or motion sickness

Giving your cat a little Benadryl before a trip so she'll sleep will keep her from getting motion sickness. However, if nausea and vomiting is the symptom you are trying to treat rather than prevent, it is best to go with another medication.

How Long Does Benadryl Take to Work?

Benadryl is a swiftly acting drug. You should see effects in less than thirty minutes. The smaller your cat is, the quicker you'll see results. The results should last a long time as well.

Generally they last eight to twelve hours. Keep your cat's size in mind when figuring out dosage. A very little cat will not need as much as a big cat. Very young kittens should perhaps not take it all. Consult with a veterinarian.


Liquid Benadryl is most recommended as it is easier to measure out. Benadryl capsules and tablets come in twelve and a half milligrams and twenty-five milligrams. This is far too much for a little cat. A milligram per pound is an acceptable dosage.

A liquid suspension of Benadryl should be twelve and a half milligrams per five milliliters. Two to four milliliters of liquid Benadryl or a little less than half a tablet should do it for an average sized cat.

For comparison, just one tablespoon is thirty milliliters, so a little bit goes a long way. This dose can be given every eight to twelve hours.

If you need a different dosage for your cat and you are having a little trouble converting milliliters to milligrams, this table should prove helpful.

  • A 2 milligram dose for a cat = 0.8 milliliter
  • A 3 milligram dose for a cat = 1.2 milliliter
  • A 4 milligram dose for a cat = 1.6 milliliter

Unless you own a tiger, it is very unlikely you will need anything bigger.

How to Give?

image of a scared kitty from the pill

Remember that a cat is much smaller than you are and does not need nearly the same dosage you would. Only give your cat Benadryl in liquid or tablet form as the topical ointment may make her sick if she licks it.

The medication must be unadulterated diphenhydramine with no other medication mixed in. Your vet can give you a syringe to squirt the medicine into Kitty's mouth.

It will be graduated so you can measure how much medicine your cat is getting. Usually, animals sick enough to need medicine won't have the energy to fight but one that's just irritated by a rash or a stung nose may be as scrappy as ever, maybe even more so.

Tablets can be crushed up and mixed in food. Your vet may offer to put in a flavor additive like chicken or fish to make the medicine more palatable for your cat. Make sure Kitty is calm before you give her Benadryl or any medicine for that matter.

Swaddling her up in a favorite blanket or towel might help. Remember to be gentle, soothing and disarming as you offer her the syringe. Don't make her think it's unpleasant. If enough flavoring is added, she may even want more, but don't give her more than needed.

When not to give this medicine to your kitty

Benadryl for Cats: How Much Should You Give & How? 1

It is also important to know when not to give Benadryl to a cat. Remember that you should treat the cause more than you treat the symptoms. If your cat is anxious or stressed out, it is better to find out why she feels this way rather than just drug her with something to make her sleepy. If your cat has heart disease always ask your veterinarian before giving her any medicine she is not already on. It is the same if your cat has glaucoma.

Take note of what other medications your cat is taking as some will not mix with Benadryl. A more detailed list of these medications will be revealed later in this article. Finally, if Kitty has been bitten by a venomous spider, snake, scorpion or other creature, she needs more than just Benadryl to treat the symptoms. She needs to see a vet right away for an anti-venom.

If your cat shows signs of anaphylaxis shock, she needs to be taken to the vet immediately signs of anaphylaxis shock include lethargy, vomiting, shortness of breath and fainting. If she has a bowel movement spontaneously and is usually good about using her litter box, something is very wrong.

Anything that looks like Kitty is having a seizure is reason to rush off to the vet. A steroid treatment and/or epinephrine will be the first thing administered. An overnight hospital stay with oxygen treatment is quite often required after having a severe allergic reaction.

Overdose & Allergic Reactions

Take care that Kitty does not overdose on Benadryl. Measure the dose precisely. Keep the medicine where she can't get to it. Some cats are allergic to Benadryl. It is expected that a drowsy cat's breathing may become slow but deep. If Kitty is panting, hardly breathing at all or fighting for air, she could be having a bad reaction to the drug.

Benadryl for Cats: How Much Should You Give & How? 4

Drowsiness is an expected side effect of Benadryl but if your cat is unusually clumsy, short of breath or having a seizure she is either allergic to Benadryl or has overdosed. Get her to the vet immediately.

Benadryl Side Effects

image of an ill feline

The reason Benadryl is sometimes used as a sedative is one of the major side effects of this medication is severe drowsiness. In a rare few cats, Benadryl may have the opposite reaction and make them hyper.

There are other reactions your cat could have to Benadryl as well. Monitor your cat to see if she experiences any of the following.

  • Loss of appetite
  • Hyperexcitability
  • Changes in urination (particularly a decrease)
  • Diarrhea
  • Disorientation
  • Dry mouth
  • Nausea or vomiting

If the symptoms are severe or do not go away on their own you may have to take Kitty to the vet. You will be told what to do to help your furry little friend. Do not exceed the recommended dosage of Benadryl as this is what leads to severe side effects.


Benadryl for Cats: How Much Should You Give & How? 4

Before you give Benadryl to your cat, take into consideration any other medicines your cat takes plus pre-existing health conditions.

Discuss things with your vet before giving your cat any medication. Also remember that Benadryl only treats the symptoms. You must also find a way to treat the underlying cause. Also remember that regular strength is sufficient. Extra strength Benadryl may be too much for Kitty to handle.

Can You Mix It With Other Medications?

Benadryl does not mix at all with any of the following medications. Do not give your cat Benadryl if she takes any of the following.

  • Amitraz This drug is often found in tick prevention medications.
  • Selegiline If your cat has cognitive dysfunction or senility she may be put on this drug.
  • Epinephrine Anyone who uses an EpiPen knows that this is for treating allergic reactions resulting in anaphylaxis.
  • Furazolidon This is often used as an antibacterial agent.
  • Heparin Sodium or Calcium This is prescribed for treatment of diseases associated with blood clotting, e.g. disseminated intravascular coagulation and thromboembolic disease.
  • Warfarin Sodium This drug is also to treat and prevent blood clots.
  • Central Nervous System Depressants Cats with anxiety disorders may be given this drug.

If your cat is on any of these medications, your vet should suggest an alternative to Benadryl. Always use caution and heed your veterinarian's advice when giving a cat medicine. This way, you can ensure that your cat is getting the best care possible.


So, is Benadryl safe for cats? Short answer, yes. But be very mindful for the dosage and its reactions.

Benadryl is a medicine you should have in every first aid kit, whether for humans or for your feline friend. Kitty is just as prone to allergies as you are. An antihistamine such as Benadryl can relieve her symptoms but keep two important things in mind. Firstly, you must treat more than just the symptoms. Secondly, your cat needs only a very small dose.

If your cat is elderly, has other health problems or takes other medication you may want to reconsider giving her Benadryl. It is for the most part a safe method of sedation but do not overdo it and try to find out first why she needs a sedative and if there are other ways to help her be calm.

Benadryl is a mostly safe medication for cats but like everything else it must only be used in moderation. Always keep in mind that a little goes a long way. Be safe, measure carefully and know when to and when not to give your cat Benadryl. This way, your cat will be healthy and happy.

Frequently Asked Questions

How useful was this post?

Click on a star to rate it!

Average rating 0 / 5. Vote count: 0

No votes so far! Be the first to rate this post.

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post?

1123 E 47th St
Chicago, IL 60653

Phone: +1 (312) 555-3890 Protection Status

Follow us:

Disclaimer is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of, Inc. or its affiliates.