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How Often Can You Give Benadryl To Dogs?

While you should always consult with your veterinarian before giving your dog any sort of human medication, some of our medicine has been deemed fairly safe for dogs to take. Benadryl is commonly used, but how often can you give Benadryl to dogs? 

Typically, a dog may have Benadryl two to three times in one day, but you should never give a dog more than one milligram of Benadryl per one pound of their weight. For instance, a twenty-five-pound dog can have one whole twenty-five-milligram tablet. 

Keep reading to learn more about how Benadryl affects dogs and how to give it to them safely. 

What Is the Dosage of Benadryl for Dogs?

Benadryl takes about half an hour to start working. According to the Merck Veterinary Manual, a safe dosage of Benadryl for dogs is one milligram per one pound of their weight, or two to four milligrams per kilogram of their weight, two to three times per day. 

However, these dosages may need to be adjusted depending on what conditions your dog may have, or what other medications they may already be taking. 

It is also important to note that tablets are the safest form of Benadryl to give to dogs. Never give a dog capsule release Benadryl, as they react to it differently, and it is easy for them to overdose on it. Small dogs can often safely be given children’s tablets or half of one. 

If all you have is liquid Benadryl, children’s is better for dogs, as it usually does not contain alcohol. Liquid dosage is trickier to calculate and difficult to generalize, so consult with your vet. Using a syringe to administer the liquid Benadryl makes it easier to measure an exact dose. 

What Will Benadryl Treat for Dogs?

Benadryl is excellent for clearing up dog allergies or symptoms that resemble those of allergies, including the following: 

  • Raised hives
  • Constant itching
  • Inflammation and swelling
  • Redness like rashes
  • Runny eyes and noses
  • Frequent Sneezing 
  • Constant Coughing
  • Milder anaphylactic reactions  

Please note that Benadryl is not enough to treat severe anaphylactic reactions like seizures. However, it also works well on dogs with anxiety or motion sickness, as it makes them drowsy. 

How Often Can You Give Benadryl to Dogs?

What Are Possible Side Effects for Dogs?

Again, although Benadryl is usually safe for dogs to have, you should check with your vet to see if this medication would interact with any other medicines your dog may be taking. Common side effects of Benadryl in dogs include: 

  • Elevated heart rate 
  • Quick breathing 
  • Dry mouth or excess drooling
  • Difficulty peeing 
  • Drowsiness

Rare side effects include the following: 

  • More or less of an appetite 
  • Vomiting 
  • Diarrhea 

Finally, signs of a Benadryl overdose include:

  • Dilated pupils
  • Sudden agitation
  • Seizures
  • Constipation

Any possible side effects or overdose symptoms are most likely to develop within the first hour of your dog taking the Benadryl, so you should watch them closely for this period. If you suspect a severe reaction or overdose, get your dog to a veterinary hospital as soon as possible. 

Which Dogs Cannot Have Benadryl?

Aside from the side effects, Benadryl can actually worsen some conditions in dogs, which is another reason why it is important to discuss whether or not your dog can have Benadryl with their vet. Dogs with the following conditions should never be given Benadryl without consultation: 

  • Pregnancy or nursing  
  • High blood pressure 
  • Seizure disorders
  • Neck or bladder obstruction 
  • Prostate gland problems
  • Closed-angle glaucoma 
  • Allergic lung diseases
  • Risk of heart failure 


Although Benadryl tends to be safe for dogs, and it is often used to effectively treat allergy symptoms, motion sickness, and anxiety, you should always discuss whether or not Benadryl is safe for your dog with a skilled vet. While Benadryl is typically great from easing long travels, it takes about thirty minutes to start working. 

Your dog may have conditions that could worsen from taking Benadryl, or it could interact with any other medicines that they are already taking. Be sure to monitor your dog for at least an hour after Benadryl starts working to ensure that they are not experiencing severe side effects or an overdose. 

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