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Benadryl for Dogs with Hives: Our Vet Explains

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Hives in dogs can be a troubling sight for many pet parents. These itchy, swollen welts can appear rapidly and cause significant discomfort for our furry friends. As a veterinarian, one of the most common questions I receive from concerned dog owners is whether they can give their dogs Benadryl to alleviate these symptoms. In this article, I’ll delve into the causes of hives, the benefits of Benadryl, and how to properly and safely use it. 

What are hives in dogs, and what do they look like?

Hives, medically termed urticaria, are a visible allergic reaction on the skin surface. Here’s how to identify hives:

  • Appearance: Raised, itchy, welts or swellings on the skin. These welts can vary in size and might merge together, forming even larger swellings.
  • Texture: They often have a palpable firmness when touched.
  • Distribution: While hives can appear anywhere on a dog’s body, they are commonly found on the legs, back, and face, especially around the eyes and muzzle.
  • Behavioral Signs: Dogs might exhibit increased scratching, rubbing against furniture, or appearing restless due to discomfort.

The appearance of hives indicates an allergic reaction. Dogs, like humans, can react to many things, such as insect bites or stings, specific foods, medications or vaccinations, environmental factors such as pollen, and chemicals present in shampoos or household items. The body’s allergic reaction leads to the release of histamines, culminating in the red, itchy welts known as hives.

Is Benadryl effective in treating hives in dogs?

Benadryl, also known as diphenhydramine, is an antihistamine crafted primarily for human use, but also effective in dogs. Its principal action is to counteract the histamine release in the body, thus decreasing allergy symptoms. 

Side effects of using Benadryl 

Although Benadryl is generally very safe, potential side effects include:

  • Drowsiness (most common)
  • Dry mouth or hypersalivation
  • Increased heart and respiratory rate
  • Gastrointestinal issues 

If you observe any unusual reactions or behaviors after giving this medication, immediately get in touch with your veterinarian.

Precautions when using Benadryl

  • Consult a Vet First: Before giving your dog Benadryl, it’s crucial to check with a veterinarian. They can provide guidance on whether it’s suitable for your dog and what the correct dosage should be.
  • Correct Dosage: Be sure that you are giving an appropriate dosage based on your dog’s weight. 
  • Check the Ingredients: Only use plain Benadryl (diphenhydramine). Some Benadryl products contain other ingredients, like alcohol, painkillers, or decongestants, which can be harmful to dogs. If using a liquid or flavored product, always check that it does not contain xylitol. 
  • Know When to Seek Emergency Care: In some cases a dog might have an anaphylactic reaction to an allergy source, or rarely to Benadryl itself. Signs of this life-threatening condition can include swelling, intense itching, rash, vomiting, diarrhea, collapse, or difficulty breathing. If you notice these or any other alarming symptoms, seek emergency vet care. 
  • Not Suitable for All Dogs: Benadryl might not be suitable for dogs with certain health conditions or who are taking certain medications. Always check with a vet.

The appropriate dosage of Benadryl for dog hives

Remember to always consult your veterinarian before giving your dog any medications. The typical dosage is 1 mg of Benadryl per pound of body weight, given by mouth every 8-12 hours. 

Alternative to Benadryl when treating hives

If Benadryl isn’t your preferred choice or if your dog shows an aversion, consider these alternatives:

  • Other antihistamines – always check with your vet, and beware of other added ingredients such as decongestants. 
  • Other oral or injectible medications such as corticosteroids to decrease itch and inflammation
  • Topical ointments or creams as prescribed by your vet
  • Preventive approaches, such as medicated shampoos, hydrolyzed protein or limited ingredient diet, and lifestyle changes to avoid common allergens

Should I consult my vet before using Benadryl to treat hives?

Absolutely. While the dosage of Benadryl for dogs is widely available on the internet, it is always best to consult with your veterinarian before giving any medication to your dog (especially those made for humans). While Benadryl is generally safe, other medications could be toxic or even fatal to our furry family members. Furthermore, in severe cases of allergic reactions, additional veterinary care beyond antihistamines will be needed. 

Veterinary treatments and prognosis for dog hives

When it comes to treating hives in dogs, veterinarians often start with antihistamines like Benadryl (diphenhydramine), as discussed above. This can be given as an oral medication or a faster-acting injection. In cases where antihistamines aren’t providing sufficient relief or the allergic reaction is more severe, steroids such as prednisone might be prescribed. These are powerful anti-inflammatories that can rapidly reduce symptoms. If hives become a recurrent issue for your dog, additional diagnostics to identify and treat the underlying allergy should be pursued. 

As for the prognosis, most dogs with hives respond well to treatment. The condition usually resolves within 24 hours of proper care. However, if a dog continues to encounter the allergen causing the hives, there’s a likelihood of the condition recurring. While hives themselves are often a surface issue, they can be indicative of a more severe allergic reaction. It’s always essential to monitor your dog and consult with a veterinarian if symptoms persist or worsen. By understanding the treatments available and collaborating closely with a vet, pet owners can ensure the well-being and comfort of their furry companions.


  • Dr. Liza Cahn, Veterinarian

    Dr. Liza Cahn is a veterinarian who graduated from Michigan State University’s College of Veterinary Medicine in 2013 with a Doctorate of Veterinary Medicine (DVM). Dr. Cahn has five years of experience working as a veterinarian in small animal practice in Washington and California. She loved working with dogs and cats and educating owners on all aspects of veterinary medicine, especially animal behavior and dermatology. She has since transitioned to remote work to be able to spend more time at home with her husband, two young kids, and two cats, and is thrilled to be able to combine her love for veterinary medicine and passion for writing. Dr. Cahn has an active veterinary license in Washington State.

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