Your four-legged feline means the world to you. Trust us, and we get it. Our cats are our family members, and we know that you would do just about anything to keep them happy and healthy. However, we likely don't have to tell you that it's not always that simple. Even the most doting pet parents can attest that sometimes problems arise that are entirely out of our hands. In these cases, cat owners find themselves wondering what to do.

One of these unpredictable health scares results from the cat experiencing an allergic reaction. Just like people, cats can experience allergic reactions to an array of things including food, vaccines, and environmental toxins. Therefore, it is essential to know what to do if such a reaction occurs.

In this article, we will cover the popular medication Benadryl. Is it truly safe for your feline friend? What are the associated adverse reactions? Knowledge is power. The more you know about preventing and treating allergic reactions, the better equipped you will be to handle the situation appropriately. Let's get to it!

What is Benadryl

benadryl package

Benadryl is a conventional medication that is primarily used to treat pain, irritation, and the uncomfortable side effects associated with allergies and allergic reactions. It typically comes in tablet and liquid form but can also be injected if the allergic reaction is severe. Sometimes, Benadryl is also used to help treat insomnia as well as nausea caused by motion sickness. 

Benadryl is one of many over-the-counter medications available that aim to ease seasonal allergies in people. However, when it comes to cats pet owners must be extremely cautious. Just because your veterinarian has deemed Benadryl to be safe in appropriate dosages, doesn't mean other drugs are also safe. (More on that in a moment)

Understanding How Benadryl Works

When histamines, also known as inflammatory substances, attach to the cells, they typically cause what is referred to as an allergic reaction. Benadryl is an antihistamine. In other words, it blocks the histamines from attaching to the H-1 receptors on the small blood vessels and smooth muscles in the cat's body, therefore, preventing an allergic reaction.

What is Diphenhydramine | Benadryl Active Ingredient

Benadryl is merely the brand name for its active ingredient, diphenhydramine. Generic Benadryl, aka diphenhydramine, can also be purchased at your local drug store and has the same effects.

Can You Give a Cat Benadryl

A question that many cat parents have is whether or not they can give their cats Benadryl. Our answer is "Yes, but...!" When appropriately administered, veterinarians agree that Benadryl is safe to give to both dogs and cats. However, there are a number of things that pet owners must be aware of before doing so!

What is Benadryl for Cats Used For

You are likely familiar with the ways that Benadryl can benefit humans. It may surprise you to learn that cats not only suffer from the identical ailments but also experience the same benefits from the medication.

Cat Allergies

Just like people, cats can suffer from allergies from just about anything that their bodies don't necessarily agree with. Unfortunately, many cat allergies develop without much warning. For instance, cats can develop food allergies to the same food they have been eating for their entire life. Additionally, things like perfume or household cleaners can also cause your cat's system to experience an allergic reaction suddenly, demanding pet owners to act fast.

Skin Allergies

Furthermore, cats can experience skin allergies that cause them to itch uncontrollably, have horrible agitation, and be extremely uncomfortable. Redness, inflammation, and bumps are often telltale signs of an allergic reaction but can be difficult to detect until the response has gotten severe. In these cases, having Benadryl on hand can be an absolute game-changer.

Reactions to Vaccines

Many cats are prone to having allergic reactions to vaccinations as well as new medications. We cannot stress enough the importance of monitoring your cat after any shots or new meds are introduced. Even cats who have never experienced an allergic reaction to certain vaccines can have an adverse response without warning. Sometimes these allergic reactions can become so severe that Benadryl alone won't be enough.

cat getting vaccinated

Bug Bites

If you live where mosquitos thrive, we don't have to tell you how awful it can be during the summer months. Unfortunately for our cats, insect bites are also a real nuisance. A single bug bite can cause weeks of scratching and itching... and when bugs bite, it's rarely only once. If you are currently experiencing mosquito bites, it's safe to say that your cat is likely being bitten, too. Make sure to keep an eye on any bites and ensure they are healing properly. The constant itching and licking can quickly cause an infection that you'll need to treat accordingly.

Additionally, many cats have a love for exploration which often leads to getting into things that they shouldn't... including beehives. If your cat is experiencing a bee sting, first, remove the stinger. Then, call your vet. Depending on the severity of the sting, they will likely recommend Benadryl.

Mild Sedative

Your veterinarian may also recommend Benadryl has a mild sedative. Most cats aren't the biggest fans of travel. Being confined to a crate for a couple of hours is enough to cause total panic. In these cases, Benadryl can be used to calm your cat and allow them to rest peacefully until you reach your final destination.

Cat Cold (Sometimes)

Finally, the common cold. Many pet owners ask whether or not Benadryl can treat a cat cold. The answer is both yes and no. Let us explain.

Benadryl can certainly prove to be useful in lessening the symptoms associated with the common cold. However, it will not cure a cold. The same goes for allergies. Taking Benadryl does not "cure" allergies. The cat will still be allergic to whatever caused the reaction. Benadryl merely inhibits the reaction. In terms of a common cold, pet owners must make sure that the cold itself is resolving rather than simply masking the symptoms. Colds often develop from bacterial or viral infections, some of which will require antibiotic treatment.  

Allergy Symptoms

In order to know when Benadryl might come in handy, it is imperative that pet owners recognize the symptoms of both allergies and allergic reactions.

The following are symptoms of allergies.


Like people, cats will sneeze if exposed to environmental allergens such as dust, pet dander, or smoke (among others). Of course, sneezing every now and then is totally normal. You should consider the possibility of allergies if your cat is sneezing much more than usual or if they sneeze when exposed to specific circumstances, i.e. sneezing every time you spray perfume.

cat sneezing


Additionally, coughing may also be a sign of allergies, particularly if your cat has a preexisting condition that affects their breathing such as asthma. Coughing, like many symptoms of allergies, is a non-specific symptom. In other words, it is a symptom of a slew of ailments. Pet owners must ensure that their cat is, in fact, coughing due to allergies and now a more serious condition affecting their lungs.  


Also, cats may wheeze when exposed to certain allergens. Again, it is imperative that cat owners make sure that their feline's breathing issues are in fact due to allergies and not a condition such as bacterial pneumonia.

Itchy, Irritated Skin

Next, a telltale sign that your feline is suffering from allergies is the presence of dry, itchy skin. A clear indicator of flea allergies is if your cat is constantly itching or biting their tail or back. Food allergies, on the other hand, tend to make the cat's head and neck itchy.

Irritated Eyes

Also comparable to people, cat allergies may cause your feline to have red, itchy eyes. You may also find a lot more eye discharge than usual. 

Careful though, cat eye discharge can mean a lot more than just allergies. You'll want to ensure that if there is an infection involved it is treated appropriately.

Ear Infections

Interestingly enough, allergies may also cause your cat to have a number of consistent ear infections as well as constant ear irritation.

Diarrhea & Vomiting

Food allergies are directly associated with gastrointestinal issues including cat diarrhea and cat vomiting. Again, these are non-specific symptoms and it is imperative that your veterinarian determines that they are in fact being caused by allergies.


Additionally, snoring is also a symptom of cat allergies. Allergens cause the cat's throat to become inflamed, thus restricting the breathing passage. As a result, snoring occurs.

Swollen Paws

Finally, you may notice your cat chewing on their feet. Upon closer inspection, you'll likely find that their paw pads are swollen. This is yet another indicator that your feline is likely suffering from allergies.

Symptoms of an Allergic Reaction

Allergic reactions can range from mild to severe but in any case, you should contact your veterinarian. In extreme cases, anaphylaxis may occur.

Anaphylaxis is a type of shock reaction that should be treated as a medical emergency. If not handled in a timely manner, anaphylaxis can lead to death.

Clinical signs of anaphylaxis shock include:

  • Excessive vomiting

  • Trouble breathing

  • Uncontrollable bowel movements

  • Uncontrollable urination

  • Seizures

  • Collapse

  • Excessive lethargy

sick cat laying down

Again, if your cat is having any of the aforementioned symptoms, emergency medical intervention is imperative right away.

Benadryl Side Effects

Now that you know the ways that Benadryl can benefit your four-legged friend, it is necessary to understand the potential adverse reactions.

  • Drowsiness and possible sedation

  • Hyperexcitability

  • Diarrhea and vomiting

  • Dry mouth

  • Changes in urination

  • Loss of appetite

If you notice any of these side effects it is imperative that you closely monitor your cat to make sure that the reaction doesn't worsen. Additionally, contact your vet. They will be able to tell you what to do next based on your cat's individual condition. Again, only give your cat the recommended dose of Benadryl. Overdoses do occur and can result in horrific, irreversible damage.

Benadryl Precautions

Additionally, it is extremely important that your veterinarian is implicitly aware of any other medications that your cat is taking before they can give the go-ahead for Benadryl use. There are some medications as well as pre-existing health conditions that may have a negative reaction to Benadryl.

If your cat is taking any of the following medications, they should not be given Benadryl.

  • Amitraz which is commonly used as a tick prevention has adverse effects when given with Benadryl.

  • Central Nervous System Depressants that are commonly prescribed to treat anxiety are known to have adverse complications when used with Benadryl.

  • Additionally, Epinephrine (a treatment for anaphylaxis) is known to have reactions with Benadryl.

  • Furazolidon, often prescribed as an antibacterial agent should not be given in conjunction with Benadryl.

  • Also, Selegiline, prescribed for cognitive dysfunction, is known to have negative interactions with Benadryl.

  • Heparin Sodium or Calcium which is used to treat diseases that involve with blood clotting both have adverse reactions when paired with the antihistamine.

  • Finally, often prescribed to treat and prevent blood clots, Warfarin Sodium should not be given with Benadryl.

If you are administering any of the aforementioned medications, there are a few options other than Benadryl that your vet will likely recommend instead. More on that in a moment.

How to Administer Benadryl for Cats

If your vet approves that Benadryl is safe for your feline friend, there are certain things you must know about Benadryl.

  • First, it is never safe to give your cat the same dosage that you would give yourself.

  • Next, the medication is always given orally in either tablet or liquid form.

  • Additionally, only give your cat pure, plain Benadryl (diphenhydramine). Check the label just to be sure no other added medication is involved as it can cause a great deal of harm.

Benadryl Dosage

The dosage of Benadryl is typically 2-4 mg for an average sized cat. For this reason, most vets recommend liquid Benadryl since such a small amount is needed and you don't want to have to break a tablet into a dozen tiny pieces. The 2-4 mg dosage can be given every 8-12 hours.

Liquid Benadryl

Most cat owners choose to use liquid Benadryl to treat their cat's allergies and allergic reactions. Liquid Benadryl is available in 12.5 mg per 5 milliliter (mL) liquid suspension and is a much more convenient way to administer the medication.

Benadryl Tablets and Capsules

Benadryl also comes in 12.5 milligrams (mg) and 25 mg tablets or capsules. Again, this is typically not the most ideal form of Benadryl as only 2-4 mg is needed for the average dose.

cat with medicine bottle

Buy a Syringe 

Additionally, we highly recommend purchasing a 1 mL or 3 mL syringe (depending on the dosage of Liquid Benadryl that your cat needs) from your local pharmacy. The syringe will ensure that you are giving the exact dose necessary. You should never estimate a dosage when it comes to Benadryl (or any other medications for that matter). Again, overdoses do occur and can be extremely dangerous for your feline.

Ask Your Vet!

Finally, it is imperative to consult with your veterinarian regarding the exact dose of Benadryl that your cat should take. Our listed dosages are merely recommended for the average cat and every cat is different when it comes to medication.

Preventing Allergic Reactions in Cats

We believe that prevention is the best medicine when it comes to just about everything. Therefore, we want to discuss a handful of preventative measures that pet owners can take in order to avoid the unpleasant realities of cat allergies.

Flea and Tick Prevention

If you live in a climate where fleas and ticks ran rampant during certain months, it is important to make sure your feline is on a regular flea and tick preventative. Fleas and ticks are of the most common sources of allergies. Taking the necessary steps to prevent an allergic reaction is key.

Changes Around The House

Additionally, allergens like grass, household cleaners, mold, and fungi are all common sources of cat allergies. Making simple household changes like replacing air filters, keeping the windows closed, and cleaning regularly can all make huge differences for your cat.

Stay Alert

Finally, one of the most important things that a cat owner can do is to stay alert. Knowing your cat's "normal" is imperative for recognizing when something is off. By simply staying alert, you can stop an allergic reaction before it becomes a full-blown issue.

Allergy Medicine for Cats: Alternatives

It is important to know that Benadryl is not the only means available to treat your cat's allergies. In fact, your vet may prescribe something totally different in order to relieve your cat's current discomfort.

Food Allergies

Diagnosing food allergies can be a bit of a challenge. You will likely have to do an elimination diet in order to figure out exactly what is causing your cat's gastrointestinal upset. However, the process is worth it. Once the food allergen is determined, simply remove it fully from your cat's diet.

Environmental Allergens

Additionally, if your cat is experiencing environmental allergies, your vet may prescribe cortisone or steroids. If the environmental allergens are unavoidable, your veterinarian may suggest using antihistamines as a preventative measure.

Insect Allergies

As far as insect allergies are concerned, your vet may recommend a medicated shampoo, topical ointment, or antibiotics for more severe cases. Additionally, if the allergic reaction is extreme, a course of steroids or antihistamines will likely be necessary.

Benadryl for Cats: The Bottom Line

At the end of the day, we know that you want the very best for your four-legged family member. In order to make sure that our animals live their very best lives possible, it is imperative that we are prepared for the unexpected. This means planning for allergies and allergic reactions.

For many cats, Benadryl is a safe and effective way to help reduce the associated side effects that often accompany cat allergies. With that being said, it is incredibly important to follow your veterinarian's guidelines for the appropriate dosage for your cat's individual needs.

Additionally, making sure that your vet is well aware of any health conditions or medications is absolutely necessary in order to make sure no additional complications arise.

Furthermore, there are several ways that pet owners can prevent and treat cat allergies without the need for conventional medication. As always, we believe that prevention is the best medicine when it comes to our pet's ailments.

Frequently Asked Questions (FAQs)

What is Benadryl?

Benadryl is a conventional medication that is primarily used to treat pain, irritation, and the uncomfortable side effects associated with allergies and allergic reactions. It typically comes in tablet and liquid form but can also be injected if the allergic reaction is severe.

How does Benadryl work?

When histamines, also known as inflammatory substances, attach to the cells, they typically cause what is referred to as an allergic reaction. Benadryl is an antihistamine. In other words, it blocks the histamines from attaching to the H-1 receptors on small blood vessels and smooth muscles, thus preventing an allergic reaction.

Can you give a cat Benadryl?

When appropriately administered, veterinarians agree that Benadryl is safe to give to both dogs and cats. Veterinarians recommend a liquid dosage of 2-4 mg for an average sized cat, which can be given every 8-12 hours.

What are signs of allergies in cats?

Redness, inflammation, and bumps are often telltale signs of an allergic reaction in cats. Other signs of allergies include sneezing, coughing, wheezing, itchy skin, irritated eyes, and ear infections.

How much Benadryl can I give my cat?

Veterinarians recommend a liquid dosage of 2-4 mg for an average sized cat, which can be given every 8-12 hours.


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