Is it safe to give my dog Benadryl?

Benadryl is an antihistamine that is mainly known for its ability to reduce itchiness from allergies as well as runny nose and watery eyes or adverse reactions to vaccines. It’s probably a medicine you have used before yourself or have given your kiddos. Luckily, for many dogs and pet owners, Benadryl is a safe medication to give for similar symptoms. It’s important to keep in mind that it may not have the same effect on a dog as on a human though since it is a human medication. But, it is a medication you can purchase over the counter or you may even have it in your medicine cabinet already.

Below you will find the following information about giving your dog Benadryl:

  1. What is Benadryl?
  2. 4 common reasons you might give your dog Benadryl
  3. How much Benadryl can I give my dog?
  4. Possible side effects of Benadryl when given to a dog

Note: This post is for informational purposes only. Benadryl can be an effective medication for dogs. As pet parents, you should always contact your vet to understand the full side effects and dosage requirements before giving your dog Benadryl.

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puppy sleeping

What is Benadryl?

Benadryl, also known as diphenhydramine, is an antihistamine that alleviates both human and dog allergy symptoms. Histamines are produced by the body in response to an allergen it wants to get rid of. Unfortunately for both humans and dogs, these allergens can cause sneezing, itching, rashes, and watery eyes.

It’s a medicine you can purchase, inexpensively, over the counter at most local grocery or drug stores. You can also grab it on Amazon here. Luckily, it acts pretty fast (within 20-30 minutes) so you can help your dog’s allergy symptoms quickly. 

4 Common reasons you might give your dog Benadryl

1 – Vaccinations

All dogs require some combination of vaccines during their life. There are vaccines that your pup is required to have for their safety and the safety and health of other dogs. You can find additional information on vaccines in this post here. 

Some dogs may experience adverse reactions to vaccines. The symptoms could be fever, swelling, or itchiness following a vaccine. If you know that your dog is likely to have an allergic reaction to an upcoming vaccine based on a past experience, speak with our vet about giving them Benadryl 30 minutes before the administration of the vaccine. Benadryl can be safe to give to your dog before or after their vaccinations to reduce their symptoms.

Wes did have a terrible allergic reaction to the leptospirosis vaccine and his entire face swelled up. I rushed him to the emergency veterinary hospital in the middle of the night to ensure his throat was not closing up. They were able to treat him with a mega dose of diphenhydramine to get the swelling down before we took him back home. They recommended over-the-counter chewable Benadryl for a couple of days to ensure the swelling stayed down. Wes was still pretty itchy but the swelling went away and I do believe that the Benadryl helped with the itching to keep him more comfortable.

If your dog is experiencing a fever, difficulty breathing or swelling of the face after a vaccine, it’s important that you contact your vet immediately. Swelling of the face and difficulty breathing are both serious symptoms that should be handled by your vet and not over-the-counter medication like Benadryl. If it’s the middle of the night, like Wes was, please seek emergency treatment. You can google ER vet and check their hours and distance from your house. Your local vet might also have emergency 24-hour vet hospital locations and contact information on their website or on their answering service.

2 – Insect Bites or Bee Stings

Your dog likely loves to be outside. Unfortunately, insects also live outside. It’s important to be mindful of mosquitos, bees, and other biting insects that live in your yard. If your dog is stung or bitten, you might notice them whining shortly after the bite. There might also be swelling in the area that the bite or sting is in.

Wes was stung by a bee once and I had no idea at first. He started to limp and then whine and then I saw a spot on his foot that was swelling up. I called my vet to see what I should do. He had told me to monitor him for the next few hours to ensure his breathing was fine but he likely would be okay. I did apply a cold compress to the string. And we just snuggled with my little guy and made sure the stinger was out as well.

puppy laying down

3 – Environmental Allergies

If your dog experiences severe seasonal allergies, they likely need something stronger than Benadryl for relief. If you know they are allergic to tree pollen or one of the many other environmental allergens, it’s a good idea to speak with your vet to discuss possible long-term allergy treatments. 

Benadryl can be used for mild cases of allergy symptoms though such as itchy skin or watery eyes. Wes used to sneeze uncontrollably for about a week when allergies kicked in here in North Carolina. But after a week he adjusted. Watch your dog’s symptoms such as scratching, sneezing, or eyes watering when allergy season rolls in to see if seasonal allergies are something that makes them uncomfortable for a long period of time.

4 – Food Allergies

If your dog is experiencing a food allergy, it is likely to be from one of the three common food allergies in dogs which are beef, dairy, and chicken. All three of these ingredients are in many store-bought dog foods and treats. Be mindful of new foods that you provide your dog or ones they may grab when you are not looking. This will help determine if their symptoms such as itching or coughing are due to a new food they ate. Providing your dog with Benadryl for a food allergy can be effective and safe, but it’s more important that you know what food they have an allergy to. This way, you can never give them the food again and ensure their food and treats don’t have that specific ingredient in them. 

How much Benadryl is safe to give my dog?

It’s okay to give smaller dogs (under 25 pounds) liquid Benadryl. Just be sure you are using children’s liquid Benadryl and avoid the grape-flavored one. Check the ingredients to ensure it does not have any dyes or any other allergens your dog might have. It may be easier to give your dog chewable tablets for Benadryl, just be sure to check the dosage. Most dosages will be based on the weight of your dog, so be sure to know their weight accurately.

For the most accurate dosage of Benadryl, please reach out to your vet. You can also find great information about the dosage and forms of Benadryl here. Benadryl should not be something you use on a regular basis unless discussed with your vet. 

Possible side effects of Benadryl when given to a dog

Although Benadryl may be recommended by your vet for mild allergies before vaccinations are given, it’s important to note the most common side effects. If your dog suffers from glaucoma, high blood pressure, heart disease, seizure disorders, gastrointestinal or urinary obstruction, or lung disease do not give your dog Benadryl. It’s important that you call or reach out to your vet before providing your dog with Bendryl to ensure it won’t interact with any other medications that your dog might be on.

Many dog owners think that Benadryl will make a dog drowsy since it’s known to have that effect on humans. This is not the case with dogs though. Benadryl can actually have the opposite effect of drowsiness with dogs and make them extra hyper. If you are thinking Benadryl is going to help with your dog’s anxiety or calm them down before car rides, think again. Speak with your vet about other safe treatments for general anxiety or travel anxiety. 

Just like any new medication, Benadryl has potential side effects. Common side effects of Benadryl include constipation, diarrhea, vomiting, increased heart rate, and loss of appetite for some dogs. Always be sure to monitor your dog closely when giving medication for the first time. It’s important that if your dog has other health conditions or is under veterinary care for anything, you speak with your vet to understand any adverse effects of Bendaryl on your dog.

liquid pink medicine


Benadryl is safe to give to your dog to help with the symptoms of allergies or adverse reactions to vaccinations. If your dog suffers from any other medical conditions or takes other medications, speak with your vet before giving your dog Benadryl to understand the safe dosage for your dog’s weight. Always be sure to monitor your dog if you suspect an allergy that may cause them to have difficulty breathing or if you notice facial swelling, contact your vet immediately.

Have you used Benadryl to treat your dog for anything? Please common below if yes and what for!