Benadryl for Dogs: Your Go-To List of Dos & Don’ts

By JoAnna Pendergrass / July 9, 2018

What is Benadryl – Understanding the Popular Medicine

Most dog owners have likely heard of Benadryl. It is an incredibly popular medication that is used primarily for alleviating seasonal allergies.

Scientifically speaking, Benadryl is an antihistamine that blocks the H1 receptors on the blood vessels and smooth muscle. H1 receptors are histamine receptors that play an important role in the allergic response. By blocking this receptor, Benadryl reduces symptoms of allergic reactions.

Additionally, Benadryl has been used to treat motion sickness in dogs and provide mild sedation.

Although many veterinarians consider Benadryl to have a wide safety margin, there are still dangers and adverse reactions associated with the drug that pet owners should be aware of.

What is Diphenhydramine

Benadryl is the brand name for the active ingredient diphenhydramine HCl.

Diphenhydramine is categorized as a first-generation antihistamine, meaning that it can cross the blood-brain barrier. The blood-brain barrier protects the brain from harmful foreign substances, such as bacteria or viruses. This barrier does allow some substances, such as diphenhydramine, to pass through.

Diphenhydramine’s ability to cross the blood-brain barrier means that it is typically very effective. However, this ability increases the risk of potential adverse reactions.

Benadryl Ingredients

Diphenhydramine is the most active ingredient found in Benadryl. As an antihistamine, diphenhydramine reduces the effects of the chemical histamine within the dog’s system.

What is Benadryl Used For?

As most pet owners know (due to their own use of Benadryl), the drug is most commonly used to alleviate allergies.

However, what some individuals may not realize is that this popular medication has several other uses.

Benadryl for Allergies

We’ll start with the basics.

When we think about allergies, we typically think about red and itchy eyes, a runny nose, sneezing, etc.

Dogs have different symptoms when experiencing allergic reactions. In most cases, dogs show allergy symptoms on the skin’s surface. Although it is possible for Fido to show signs of allergies that are similar to those of humans, you’ll want to make sure that your pup doesn’t have a more serious condition at hand.

Nasal discharge, coughing, and inflamed eyes can be a sign of a slew of conditions in dogs, including respiratory infections. Therefore, it is important not to automatically assume that allergies are causing these symptoms.

The bottom line is that your dog can absolutely suffer from allergies. Your veterinarian may recommend Benadryl to alleviate your dog’s allergy symptoms.

Allergies in dogs include:

  • Seasonal allergies
  • Food allergies
  • Environmental allergies
  • Allergic reactions to snake bites
  • Allergic reactions to insect bites

Unfortunately, despite how badly we wish it were possible, we aren’t exactly able to communicate with our dogs in a clear, concise way. They can’t let us know when something in the air, or in their food, is making them feel funny.

We also can’t describe to them how badly ant bites feel and tell them to avoid those fun-looking mounds in the grass.

For this reason, knowing that Benadryl is safe for dogs (to a degree) makes many dog owners feel at ease if their adventurous pup is prone to itchy situations.

With that said, we want to stress that, as in humans, allergies and other conditions can be mistaken for one another.

For example, you’ll want to ensure that your pup is suffering from allergies and not a skin infection, as Benadryl is not an effective way to treat skin conditions. Your veterinarian will be able to determine whether your dog has an allergy or skin infection.

Benadryl for Hives

Benadryl is also known to effectively treat hives in both dogs and humans. In dogs, most cases of hives are merely due to allergic reactions of one kind or another.

In humans, hives can be a symptom of several underlying medical conditions, so treating it with a medication such as Benadryl will work for the immediate relief, but not as a long-term treatment and certainly not as a cure.

Although pets with hives may look pretty miserable, we want to implore pet owners not to panic if Fido breaks out in hives, as the hives can be treated, typically without any complications.

Benadryl for Anxiety

A major side effect of diphenhydramine, the active ingredient in Benadryl, is drowsiness. If your pup has anxiety, your veterinarian may prescribe Benadryl to help ease symptoms of anxiety and effectively help your anxious pup calm down.

Benadryl for Motion Sickness

Many pet owners may not know that Benadryl is often recommended for dogs who experience motion sickness.

Treating Mast Cell Tumors with Benadryl

Mast cells are white blood cells that play a role in allergic reactions. When a dog has mast cell tumors, there is a mast cell degranulation, which causes a massive histamine release.

If your dog has a mast cell tumor, your veterinarian may recommend Benadryl to alleviate symptoms from the histamine release from the tumor cells.

Benadryl in Heartworm Treatment

Heartworm treatment involves the killing of adult heartworms. The death of the heartworms can trigger a serious allergic reaction. If your pup has to undergo heartworm treatment, your vet may recommend Benadryl to ease the symptoms associated with the treatment.

When to Call The Vet — Allergic Reactions

Many veterinarians and pet owners find Benadryl to be an effective antihistamine for mild to moderate allergic reactions.

However, if your pup is having an acute allergic reaction with facial swelling or difficulty breathing, it is imperative that you go straight to the vet.

Benadryl is not effective in serious cases of allergic reactions. Seeking medical intervention in a timely manner is extremely important for your dog’s life if he’s having a serious allergic reaction.

Benadryl Dosage for Dogs

We want to note that Benadryl is typically administered in the tablet form when prescribed for dogs. Liquid Benadryl can be mixed in with your dog’s food only if your vet deems it safe to do so. Dog owners should consult with their vet first.

Benadryl dosage is based on the dog’s body weight. We have included a general guide for administering Benadryl.

For dog owners who want a more accurate dose, experts say that 1mg of Benadryl per 1lb of body weight is the way to calculate the amount of Benadryl that will be safe and effective.

How Much Benadryl Can I Give My Dog

30lbs or smaller                                 10mg per dose
30 – 50lbs                                          25 mg per dose
50lbs or over                                      50mg per dose

The amount of times you can give the medication to your pet is typically around 2 – 3 times a day, 8 hours apart. Benadryl typically takes effect within 30 minutes of administration.

We don’t have to tell you that no two dogs are the same. All dogs respond differently to new medications in their lives.

Therefore, it is incredibly important to talk to your veterinarian about the dose that is right for your particular pooch.

Benadryl for Dogs — Is It Safe?

Although Benadryl has been deemed to be safe when used appropriately, there are a few things that dog owners should be aware of.

When to Avoid Benadryl

Dogs with glaucoma, high blood pressure, and cardiovascular disease should avoid Benadryl, as it can worsen their condition.

Furthermore, dogs with the following conditions should not receive Benadryl:

  • Angle-closure glaucoma
  • Allergic lung disease
  • Bladder neck obstruction
  • Heart failure
  • Prostatic hypertrophy
  • Pregnancy
  • Nursing
  • Hyperthyroidism
  • Seizures

Benadryl Side Effects

As with all medications, Benadryl comes with quite a few unpleasant side effects.

Common Side Effects of Benadryl

  • Dry mouth
  • Urinary retention
  • Increased heart rate
  • Sedation
  • Hypersalivation
  • Rapid breathing

Additional (More Uncommon) Benadryl Side Effects

  • Increased appetite
  • Decreased appetite
  • Vomiting
  • Diarrhea

Benadryl Overdose

Benadryl causes hyperexcitability of the dog’s central nervous system. It is critical to seek proper medical attention if you think that your dog may be experiencing an overdose.

Additional signs of a Benadryl overdose include:

  • Dilated pupils
  • Seizures
  • Rapid heart rate
  • Irregular heartbeat
  • Agitation
  • Confusion
  • Constipation
  • Muscle tremors

Diphenhydramine Side Effects

Again, we want to reiterate that diphenhydramine, as the active ingredient of Benadryl, comes along with the same risks and potential adverse reactions as Benadryl.

Home Remedies For Dog Allergies

Luckily, as a pet owner, you have options! There are some extremely effective and safe alternatives to Benadryl that may support skin health and other ailments.

In fact, the alternatives we are about to list come with virtually no side effects. Take a look!

Oatmeal Bath

Oatmeal can serve as a soothing home remedy for irritated and itchy skin, provided that your dog isn’t allergic to oatmeal (wouldn’t that be a mess). All you have to do is mix plain oatmeal and water and apply to irritated skin. Or, you can draw a bath (we recommend using our Bath Assistant if your dog is not a fan of the tub) and add the oatmeal directly to the water. Let your pup soak for 10 minutes to put their itchy skin at ease.

Coconut Oil

You can give your dog coconut oil to soothe irritation and even prevent parasites. Look for coconut oil that is high in lauric acid, which will make it more effective. To use it, apply a small amount directly to your dog’s coat or simply feed it to them.

If you choose to feed your dog coconut oil, start with feeding a small amount (¼ teaspoon for small dogs and 1 teaspoon – 1 tablespoon for large dogs) 1 – 2 times per day with meals.


Because skin irritation is so common in our furbabies, we created CBD-infused coconut oil for dogs and cats!

Talk about a double whammy! Our coconut oil is definitely a fan-favorite.


You can also use pure, full-spectrum CBD oil. Studies suggest that CBD oil supports skin health, particularly for animals with sensitive skin.

Honest Paws full-spectrum CBD oil is all-natural, soy-free, non-GMO, and lab-tested. We offer three different levels of CBD oil, based on your dog’s weight.

CBD oil can be squirted straight into your pup’s mouth, mixed into their food, or – if you’re a fan of baking – baked into their favorite homemade treats.

Restore CBD Dog Treats

If you’re not a top chef who makes homemade dog treats (no judgment here), we recommend our coconut flavored Restore CBD dog treats. These strain-specific treats include a terpene profile that supports healthy skin and a healthy coat. 

These melt-in-your-mouth morsels are definitely a fan favorite.

Benadryl for Dogs: The Bottom Line

One of the worst feelings that a dog owner can experience is watching their beloved furry companion suffer.

On top of that, sifting through the seemingly endless lists of medication and drug options can be incredibly frustrating. What is safe? Which option has the least amount of side effects? Is it possible to ease symptoms without the potential for additional problems and adverse reactions?

We understand how stressful it can be. Although medications like Benadryl may be “safe” for short-term treatment, it is comforting to know that it’s not the only solution. We encourage our readers to explore all-natural options like CBD.

Fido will thank you for it!



About the author

JoAnna Pendergrass

JoAnna Pendergrass, DVM is a veterinarian and freelance medical writer in Atlanta, GA. After earning her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine, she pursued a non-traditional career path as a veterinarian. JoAnna completed a 2-year postdoctoral research fellowship in neuroscience at Emory University’s Yerkes National Primate Research Center, then became a medical writer. As founder and owner of JPen Communications, a medical communications company, JoAnna is passionate about educating pet parents about pet care and responsible pet ownership. Although she does not currently have any pets to call her own, she loves living vicariously through other pet parents and watching Nat Geo!