Dog Knowledge

Benadryl For Dogs: Dosage, Benefits, & Side Effects

Written By: Tiffany Ruiz Dasilva, VMD, cVMA | Professional Services Veterinarian, Wild Earth

NOTE: It is best to contact your veterinarian for guidance before administering any medication to your pet.

If your dog suffers from mild allergies or is experiencing an allergic reaction from an insect bite or sting, for example, it may surprise you to know that you can reach to your medicine cabinet for help. While other human drugs should NOT be used on our canine companions, Benadryl, when given in the correct dose, is generally safe to use, well tolerated and has a low risk of overdose in dogs.

What is Benadryl

Benadryl, also known by its active ingredient 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, triggering sneezing, itching, etc. Benadryl works by blocking histamine receptors, in turn, reducing allergy symptoms. It is important to bear in mind that Benadryl is not as effective for dogs as it is for humans, and is typically only mildly to moderately effective in alleviating mild allergy symptoms. 

In this article, I will discuss when you can give your dog Benadryl, the proper dosage according to body weight, and its potential side effects.

Can I Give My Dog Benadryl? 

Yes, you can give your dog Benadryl as long as you do not exceed the recommended dosage or frequency. It is also important to make sure that diphenhydramine is the only active ingredient in the product, as sometimes antihistamines can be combined with other ingredients which can be toxic to dogs. 

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What Can Benadryl Treat In Dogs?

Benadryl is typically recommended by veterinarians for dogs experiencing mild allergic symptoms caused by insect bites or stings, medications or vaccinations. It can be given to dogs prior to vaccination for those who typically experience a reaction. If your dog is experiencing an allergic reaction that is accompanied by facial swelling or difficulty breathing, please contact a veterinarian immediately as this can be life threatening.

Benadryl can also be used to treat symptoms of environmental, flea or food allergies. While veterinarians generally approve of using Benadryl for dogs with mild allergies, it is important to keep in mind that Benadryl is not as effective for dogs as it is for humans, and it should not be used to treat severe allergies. Additionally, if your dog is experiencing a food allergy, it is likely due to one of the top food allergens in dogs which are beef, dairy, and chicken, and removing the offending food is key. 

The most common symptoms that Benadryl can help alleviate:

  • Hives
  • Itchy, red, inflamed skin
  • Swelling and inflammation
  • Red, itchy eyes
  • Sneezing
  • Coughing or hacking
  • Runny nose
  • Itchy or red ears

While Benadryl can be used for motion sickness, there are more effective over the counter options for motion sickness than Benadryl. If your dog is experiencing motion sickness, speak with your veterinarian.

How Much Benadryl Can I Give My Dog?

The amount of Benadryl that you can safely give to your dog will be impacted based on your dog’s weight, the symptoms they are suffering from, and their current health condition. The standard dosage for a dog is 1 milligram per pound of body weight. This number is a guideline and you should speak with your veterinarian before giving your dog Benadryl, as they have a better understanding of your dog’s current health and how an antihistamine will impact your dog.

Recommended Benadryl Dosage for Dogs

Most drugstore diphenhydramine tablets, whether generic or brand name Benadryl, are 25 milligrams. As with any drug, the correct dosage of Benadryl for dogs depends on the dog’s weight.

Benadryl Dosage for Medium-to-Large Dogs

The standard dosage for a dog is 1 milligram per pound of body weight, so one tablet is perfect for a 25-pound dog. Veterinarians suggest giving a dose every 8-12 hours (about 2-3 times a day).

Benadryl Dosage for Small Dogs

Small dogs under 25 pounds can take the children’s formula of liquid Benadryl. Liquid children’s formula is easier for measuring the proper dosage for smaller dogs than tablets, and can be given at a dosage of 0.4 mL/lb. Stick to the children’s formula of liquid Benadryl as the adult version contains alcohol, which is toxic to dogs. Additionally, avoid grape flavored formulations.

Benadryl Dosage Chart For Dogs


Guidelines For Benadryl For Dogs

It is important to follow the dosing and frequency recommendation when giving your dog Benadryl as overdose is possible. Abuse of the drug can result in fatal diphenhydramine poisoning, so always consult your veterinarian if you are unsure of the proper dosage. Signs of overdose can include excitement, seizures, lethargy, rapid heart rate, and decreased respiration.

If your dog is suffering from an onset of a severe allergic reaction, use your best judgment to determine if it would be best to opt for an emergency trip to your veterinarian. If you notice any facial swelling or difficulty breathing, take them to your nearest emergency veterinarian. 

Again, make sure to select a product which lists only diphenhydramine as the active ingredient. Avoid using time-release capsules for dogs. Time-release capsules are absorbed differently in humans vs dogs and may affect your dog’s dosage. Also, be extra cautious when using Benadryl in older dogs as they may be a bit sedated and/or confused.

Benadryl Side Effects in Dogs

Just like any medication, Benadryl comes with potential side effects. Common side effects of Benadryl include constipation, sedation, urinary retention, 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.

How Long Does It Take For Benadryl To Work In Dogs?

Benadryl, or Diphenhydramine, typically takes effect in under an hour.

When to Avoid Giving Your Dog Benadryl

Do not use Benadryl if your pet suffers from the following diseases: glaucoma, high blood pressure, cardiovascular disease, seizure disorder, gastrointestinal or urinary obstruction, or lung disease. Benadryl may negatively interact with other medications, for example, central nervous system depressants. Make sure to consult your veterinarian before giving Benadryl if your pet is on any medication. If your dog is having difficulty breathing or swelling in the facial area, take them to the vet immediately. 

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Is Benadryl Safe For Dogs To Calm Them Down?

Many dog owners will use Benadryl to calm their dogs down as it causes drowsiness in humans. Although Benadryl causes drowsiness in humans, it can have the opposite effect on dogs and cause hyperactivity instead of sedation, therefore Benadryl is not recommended for anxiety. If your dog does suffer from anxiety, is fearful of fireworks, or gets nervous when traveling, it is important to consult with your veterinarian as there are much better options such as calming supplements and medications, training, pheromones, etc.

Can I Give My Dog Liquid Benadryl?

Liquid Benadryl should only be used for small dogs, as the amount for a large dog would be large. If choosing liquid Benadryl, make sure to choose the children’s liquid Benadryl as the adult formulation may contain alcohol. Also, make sure to avoid grape-flavored medications. 

Liquid Benadryl or tablets will both list how many milligrams are within one serving. You should use this number as a reference in order to give your dog the correct and safe amount. It is important to be aware that liquid Benadryl will be in mg/mL (instead of mg/tablet) and therefore a little math will be necessary to figure out how many mL to give your dog. Brand name children’s Benadryl is typically 12.5 mg/5 mL, meaning that you will need to give 5 mL of liquid to deliver 12.5 mg to your dog. This can be given at a dosage of 0.4 mL per pound. 

Dog Allergies: Causes and Treatment

Believe it or not, your dog’s allergy symptoms might be from the food they’re eating. The animal-sourced ingredients in dog food (beef, dairy, chicken, lamb, egg, pork, fish, and rabbit) are responsible for over 3 times as many food allergy cases as the plant-based ingredients. According to a study published on, after five weeks of their dog patients “starting an elimination diet, more than 80% of patients had achieved a remission of clinical signs of CAFR [Cutaneous Adverse Food Reactions].”

That means your dog’s allergies could be eliminated just by changing what they eat. So before you give your dog any Benadryl for a suspected food allergy, consider switching their dog food. 86% of customers reported a positive health benefit for their dog after switching to Wild Earth dog food!

We have thousands of reviews from customers whose dogs no longer suffer from chronic itching, licking, inflammation, or gastrointestinal problems because of switching to Wild Earth dog food. Check out one of them in the video below!

Tiffany Ruiz Dasilva, VMD, cVMA

Dr. Tiffany Ruiz Dasilva is the Professional Services Veterinarian here at Wild Earth. She received her Bachelor of Science degree in Biology from Brown University, and attended veterinary school at the University of Pennsylvania School of Veterinary Medicine. Since graduation, she has worked in general practice, on telehealth platforms, and in animal rehabilitation. She has worked tirelessly to gain expertise in the field of canine nutrition through numerous certifications and coursework, and plans to pursue her Masters in Animal Nutrition.

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