Antihistamine For Dogs – What You Need to Know?


You may have heard that some over the counter medications for people, such as antihistamines, are safe for dogs to use. What do you need to know about using an antihistamine for dogs before using one on your own dog? Are they safe? What are the common uses? Which one should you use for your dog? How do you dose it?

You should always discuss over the counter medication use with your veterinarian first. Here’s a brief rundown of everything you need to know about using an antihistamine for dogs so that you can talk to your vet about whether or not it’s the best treatment option for your dog.

Antihistamines for Dogs

#1 – Are antihistamines safe for dogs?

Generally speaking, antihistamines are safe for dogs. They come with fewer side effects than other treatment options for allergies such as corticosteroids. There is a slight chance of side effects, but they are usually mild. Common side effects that may occur as a result of using an antihistamine for dogs include:


-Dry mouth

-Urinary retention


Sleepiness, drowsiness, and sluggishness are the most common side effects of using an antihistamine for dogs, especially Benadryl. If given regularly, dogs usually overcome the sleepiness within a few days.

Are antihistamines safe for dogs

Less common side effects from using an antihistamine for dogs include:



-Loss of appetite

-Allergic reaction


These side effects are more severe and you should discuss them with your veterinarian.

Benadryl For Dogs

While using an antihistamine for dogs is usually safe, there are some dogs who you should not treat with them except under direct advice from and supervision of a veterinarian. Dogs who should avoid antihistamines include dogs who:

-Are pregnant or nursing

-Are puppies

-Have glaucoma

-Suffer from urinary retention

-Have high blood pressure

-Suffer from a cardiovascular disease

-Have liver problems

Dog sleeping pill

#2 – What are they used for?

Veterinarians commonly recommend antihistamines for allergies, especially environmental allergies such as pollen, bee stings, or flea bites. Food allergies are better treated by using limited-ingredient diets to identify and eliminate problem foods and ingredients.

Antihistamines can also be given before vaccinations to reduce the risk of a dog having an allergic reaction to the vaccination. Benadryl, the most common antihistamine for dogs, has more sedating side effects than most other antihistamines for dogs. It’s therefore also commonly used to reduce anxiety, such as during fireworks or travel, and to reduce the symptoms of motion sickness.

Talk to your veterinarian to see if your dog’s symptoms might be lessened by the use of an antihistamine.

Antihistamine for dogs anxiety

#3 – How do antihistamines work?

Histamine is a chemical released by mast cells inside your dog, typically as a reaction to an allergen (although mast cell tumors will also release excessive amounts of histamine). Antihistamines block the receptors for histamine, preventing the histamine from causing your dog allergic symptoms.

Allergic symptoms may include itching, sneezing, scratching, chewing, runny eyes, red skin, and hair loss. Antihistamines in general, and Benadryl in particular, have about a 30% success rate in treating allergies in dogs. They are a safer alternative than the next level of treatment, corticosteroids.

Steroids may cause severe and permanent side effects, so it’s always worth trying each variety of antihistamine for dogs to see if they help reduce symptoms.

Stop dog anxiety

#4 – Which one should I use for my dog?

Diphenhydramine, the active ingredient in Benadryl, is the most common antihistamine for dogs. It seems to be the most effective antihistamine for dogs and is relatively well-tolerated. It isn’t the only option if your dog doesn’t tolerate it well. Cetirizine, hydroxyzine, chlorpheniramine, cyproheptadine, trimeprazine, and clemastine are other commonly-recommended antihistamines for dogs. Your veterinarian should be able to recommend that best antihistamine for your dog’s condition.

#5 – How do I dose an antihistamine for dogs?

You should always discuss over the counter medication use with your veterinarian. With that being said, the typical dose of diphenhydramine (Benadryl) is 1 mg of medication per pound of your dog’s body weight. Tablets typically come in 25 mg doses, so one tablet would be perfect for a 25-pound dog. 2 tablets would be ideal for a 50-pound dog, and half a tablet would work for a 12-pound dog.

Slow release capsules are not recommended. Dogs digest them at a different rate than humans and may get too much or not enough of the active ingredient.

can i give my dog antihistamines

Liquid dosing of Children’s Benadryl may be a better option for smaller dogs. Never use adult versions of liquid Benadryl as they may contain alcohol or Xylitol, both of which are toxic for dogs. When giving liquid Children’s Benadryl (preferably dye-free), the dosing is different than tablet dosing.

The usual concentration of liquid Children’s Benadryl contains 12.5 mg of the active ingredient, diphenhydramine, per 5 mL dose. You should give it at a dosage of 0.4 mL per pound of your dog’s weight. That means that a 10-pound dog should receive 4 mL of liquid. A measuring teaspoon contains 5 mL, so you may want a syringe for more accurate dosing. While human kids may enjoy the flavors of Benadryl, dogs usually don’t, so it is preferable to use the tablets if you can.

Whichever dosage form you prefer, Benadryl can safely be given 2-3 times per day.

Dosages for other antihistamines will vary and should be discussed with a veterinarian prior to use.

Are antihistamines safe for dogs

#6 – What else do I need to know?

Some formulations of antihistamines may contain other ingredients than just diphenhydramine or another antihistamine. These ingredients treat things such as sinus infections, colds, or insomnia in people. These other ingredients may be toxic to dogs and you should avoid them. You’ll want to make sure that the only active ingredient when selecting an antihistamine for dogs is diphenhydramine, or whichever antihistamine you choose, and nothing else.

Dogs whose symptoms are well-managed on antihistamines may become acclimated and need higher doses in the future. Always discuss increased dosages with your veterinarian. Eventually, your dog may become so acclimated that it’s best to try a new method of treatment.

Your veterinarian knows your dog and his symptoms best and should always be your first resource when considering an antihistamine for dogs.


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