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Benadryl for Dogs: What You Need to Know

As much as pet parents love their dogs as they would their own children, it’s important to remember that not not everything that’s suitable for humans is safe for canines. This is especially true for medications - even when it seems that what ails your dog is very similar to a human health condition. 

There are, however, some human medications - mostly over-the-counter ones - that can be used safely and effectively as treatment for certain doggy symptoms. One of the most commonly prescribed by veterinarians is Benadryl, also known generically as diphenhydramine. 

Benadryl for Dogs: What is it used for?

A wide range of symptoms in dogs respond well to Benadryl. These include:

  • Food allergies; environmental allergies; seasonal allergies; allergic reactions to insect bites, snake bites, and medications
  • Hives
  • Mild to moderate anxiety or stress, especially when travelling, when exposed to fireworks, or during thunderstorms
  • Motion sickness
  • Mast cell tumors

Benadryl is yet to be approved by the FDA for veterinary use, but it is considered a relatively safe treatment for cats and dogs. If you have not yet done so, you should include Benadryl in your dog’s emergency kit and travel kit; or just make sure to keep liquid Benadryl for puppies and small dogs or Benadryl tablets for big breeds and adult dogs in your medicine cabinet. 

How Does Benadryl Work?

When used as treatment for allergies, Benadryl works the same way in dogs as it does in humans - by blocking the receptors that trigger allergic symptoms. Benadryl effectively reduces common allergy symptoms, such as itching, hives, runny nose and eyes, sneezing, coughing, swelling and inflammation, and even anaphylaxis. The medication typically takes effect after 30 minutes of being administered. 

Because drowsiness is a common side effect of Benadryl, veterinarians recommend this medication to help calm dogs when they’re feeling moderately anxious or stressed. Travel-related anxiety, as well as motion sickness, can be effectively alleviated with Benadryl.

Benadryl’s antihistamine action - wherein it blocks histamine receptors - also makes it a good adjunct therapy for conditions and treatments that involve a massive release of histamines, leading to allergic reactions. 

How to Use Benadryl for Dogs

Your dog’s weight will determine the right dosage of Benadryl to give him, and whether tablets or liquid Benadryl is suitable. 

Benadryl tablets are for dogs that weigh 25 pounds or more, and the recommended dosage is 1 mg per pound of body weight (or 2 to 4 mg per kilogram of body weight). The standard weight for a diphenhydramine tablet is 25 mg, so one tablet is enough for a 25-lb dog, given every 8 to 12 hours, or as prescribed by your veterinarian.  

Liquid Benadryl for kids is ideal for dogs under 25 pounds, as it is easier to measure the proper dosage and smaller dogs are more susceptible to an overdose. Adult or bigger dogs can also suffer from an overdose if too much Benadryl is given to them, so always consult your vet to know the proper dosage. Signs of diphenhydramine poisoning that you should watch out for include:

  • Agitation
  • Constipation
  • Dilated pupils
  • Erratic or rapid heartbeat
  • Seizures 

Take Fido to a vet immediately if you suspect an overdose as it could become fatal. 

Some allergy symptoms may also be caused by a more serious condition that will worsen if not treated properly right away or if the wrong medication is given. Red and itchy eyes, for example, could be caused by dry eye or glaucoma, neither one of which would not respond well to Benadryl. It’s always best to take Fido to a vet before reaching for the Benadryl. If you are unable to go to a vet and you decide to give your best bud Benadryl for his symptoms, watch out for any adverse reactions - stop giving him diphenhydramine if you notice any and take him to the vet as soon as possible, especially if his condition takes a turn for the worse. 

What are the side effects of Benadryl?

Even with the proper dosage, Fido might experience some mild side effects with Benadryl treatment. More serious side effects often indicate an overdose or an adverse reaction to other medications or due to an underlying or pre-existing condition. You should notice the side effects, if there are any, within the first hour after you administer the drug.

Common side effects of Benadryl use in dogs that you should be aware of are as follows:

  • Sedative effects
  • Dry mouth
  • Hypersalivation
  • Rapid breathing
  • Rapid heartbeat
  • Urinary retention

Less common side effects which can be harmless if they do not persist but should warrant immediate veterinary attention if they do not improve after one or two days include:

  • Poor or increased appetite
  • Diarrhea
  • Vomiting 

Do not give your dog Benadryl unless prescribed by your vet if your furkid is pregnant or nursing, or has any of the following: 

  • Hypertension
  • Glaucoma
  • Heart failure
  • Prostate disease
  • Bladder problems
  • Seizure disorders
  • Lung disease

Severe allergic reactions may require a more fast-acting antihistamine treatment which only a vet can administer. Carefully gauge if and when your dog needs emergency attention based on his symptoms. Additionally, if your dog’s allergy symptoms worsen after being given diphenhydramine, he may be allergic to Benadryl.

Is it safe to give your dog Benadryl?

When used properly and if your dog is in good health, Benadryl is a relatively safe medication. If it’s Fido’s first time taking Benadryl, keep a close eye on any symptoms or adverse reactions that might appear. If your dog is taking other medications, has a pre-existing condition, or is pregnant or nursing, consult your vet before giving your pooch diphenhydramine. 

What natural alternatives can you give your pooch aside from Benadryl?

There are natural remedies you can give Fido to relieve his allergy symptoms or motion sickness. It’s still better to be safe than sorry, so always consult your vet whenever possible before starting a new treatment regimen. 

Baking Soda

Used as a topical application, baking soda is a great natural remedy for mild skin conditions, such as redness, itchiness, or inflammation. You can make a paste or a spray solution, and simply apply or spray the baking soda on the affected area. Cover the treated area or have Fido wear a cone if he has a tendency to lick it. 

Cannabidiol (CBD)

Don’t worry, CBD does not contain the psychoactive compound, TCH, which is present in marijuana. CBD is derived from agricultural hemp and is considered safe for dogs. It works well in treating skin allergies, such as itchiness and dryness, as well as anxiety, nausea, and motion-sickness. This natural remedy is available as tablets, balms, lotions, and oils. 


This is an anti-inflammatory, antihistamine, and antioxidant compound found in the skin of fruits and vegetables. Of course, make sure the plant food is dog-friendly! Blueberries, strawberries, and spinach are a few of your options. Quercetin is nature’s Benadryl, and works great in relieving itchy and red eyes, sneezing, inflammation, and runny nose. 

The recommended dosage can be calculated by using the 1,000-mg dosage for a 150-pound adult human. Just multiply your dog’s weight by 1,000 mg and divide by 150. 

Benadryl for Dogs: Final Thoughts 

You should have Benadryl handy to help treat your otherwise healthy dog’s allergy symptoms - from food, the environment, or insect or snake bite; it also works well in relieving anxiety and motion-sickness. This over-the-counter medication is commonly recommended by veterinarians as a safe and effective remedy for the aforementioned conditions. 

Be aware of the symptoms that you should watch out for and which would require immediate veterinary attention. When in doubt, always consult your vet first. There are also a few natural remedies that you can give your pooch if you’re wary of using Benadryl.