Benadryl Dosage for Dogs

Giving any medicine to your dog can be a nerve-wracking experience. You need to make sure it’s safe, effective and won’t cause more harm than good.

Generally, you want to avoid giving “people medicine” to dogs. However, Benadryl can be safe if used properly. Here’s the rundown on giving your dog Benadryl – why you might want to and how to do so safely:

What is Benadryl?

Benadryl is an over-the-counter antihistamine. It blocks H-1 receptors found on smooth muscle and blood vessels. Those receptors can react to a wide range of allergens such as pollen, animals, dust mites and more. Unwanted reactions include sneezing, itchiness, hives and similar symptoms.

People use Benadryl mainly for allergy relief. It’s available in both tablet or liquid form. Benadryl is a brand name for the antihistamine diphenhydramine. You can find a variety of generic versions of diphenhydramine at most grocery and discount stores.  

Diphenhydramine treats seasonal allergies, such as hay fever during the summer. It also treats specific environmental allergies such as a pet allergy.

Why Do Dogs Need Benadryl?

Just like with people, Benadryl is mainly given to dogs to treat allergy symptoms. It’s also commonly used as a:

  • Mild sedative
  • Motion sickness treatment
  • Pre-treatment to prevent vaccine reactions
  • Treatment for reactions to insect stings or bites

Here’s a closer look:

Dog Allergies

Dogs suffer from many of the same types of allergies as people do. Generally, dog allergies are divided into two separate groups:

  • Atopy
  • Food allergies

Atopy allergies are those caused by inhaling pollens or other airborne material. It’s a lot like hay fever, only for dogs. They can be allergic to something seasonal, like pollen from a plant which blooms in the spring.

Aside from seasonal allergies, dogs can also be allergic to something in their environment. Dust mites are a common indoor allergen.

People with atopy allergies typically suffer from sneezing, congestion, red eyes and other sinus-related issues. Dogs are different. They get skin problems.

Symptoms of Atopy Allergies

Watch for frequent or intense scratching. Your dog might also lick or chew his limbs, paws or tail. Some dogs rub their heads against the furniture or floor.

Itchy skin is often the primary symptom, but secondary problems can quickly develop. Infections, especially in the ears or anal glands, are commonly caused by excessive scratching. Hair loss is also possible. Secondary symptoms are often easily treated but will keep returning until the underlying allergy problem is addressed.

Diagnosing Atopy Allergies

The cause of the allergies needs to be determined before treatment can begin. You and your vet will work together to identify what exactly your dog’s allergic to.

Symptom timing can be a helpful clue. Environmental allergies are likely if your dog displays symptoms year-round. Seasonal allergies only cause symptoms during certain parts of the year.

Skin tests are the most accurate diagnostic tool. They work just like allergy tests for people. The vet will scratch small amounts of potential allergens into your dog’s skin. He or she will then closely monitor the skin’s reaction to each substance.

While accurate, skins tests are also unpleasant, time-consuming and expensive. They’re usually only given to dogs with severe allergy problems.

Treating Atopy Allergies  

Moderate to severe allergies typically require a multi-faceted approach:

  • Allergy shots to help build up a natural resistance
  • Reducing exposure to the allergen as much as possible
  • Symptom treatment

A skin test is needed to determine the contents of the allergy shot.

Mild to moderate allergies respond to simpler treatments:

  • Reduced exposure to the allergen (always a good idea)
  • Frequent bathing
  • An increase of Omega-3 fatty acids in the diet
  • Antihistamines

Benadryl is most effective at treating seasonal atopy allergies of mild to moderate severity. It also treats environmental allergies. However, ultimately, you’ll be better off treating environment allergies by changing or cleaning the environment instead of treating the symptoms with the year-round use of antihistamines.

Food Allergies

About 10% of dogs have food allergies. Dogs develop food allergies over time. In most cases, they’ll become allergic to the food they’d previously eaten without incident for years. Most allergies are caused by the protein in the food, although some food allergies are caused by grains.

Food allergy symptoms include skin issues such as itchiness and hair loss. But most of the symptoms will likely be gastrointestinal. Watch for frequent vomiting, diarrhea, constipation, and similar issues.

Treatment for food allergies usually involves switching your dog’s food. You’ll use a process called an elimination diet. Slowly replace your dog’s existing diet with new food consisting of a different primary protein.

If symptoms subside after about a month on the new food, you’re likely dealing with an allergy. However, you’ll need to confirm the allergen by switching back to the old food. If symptoms return, you’ll switch back to the new food.

Benadryl can sometimes help reduce symptoms for food allergies, but it doesn’t treat the underlying cause. You’ll likely notice symptom flare-ups after the antihistamine wears off. Food allergies require a diet change; Benadryl isn’t a long-term solution.

What Dosage of Benadryl is Safe for Dogs?

Always consult with your vet for specific dosing instruction.

The Merck Veterinary Manual recommends a dose between 0.9 and 1.8 milligrams of diphenhydramine for every pound of body weight. Most people round this off to 1 mg per pound of dog.

You can give diphenhydramine to a dog up to three times a day. Each dose lasts between four and six hours.

Standard tablets contain 25 mg of diphenhydramine. That’s appropriate to give to a 25-pound dog. However, it’s generally not a good idea to split tablets up for small dogs. Dosing can be dangerously imprecise. Only give full tablets to appropriately large dogs.

Benadryl is also available in 50 mg doses. Generally, that’s too much for most dogs, unless your dog weighs over 50 pounds. However, 80 mg is the dosage limit for all dogs, even ones which weigh more than 80 pounds.  

Liquid diphenhydramine is usually the best option. It’s the easiest form of Benadryl to measure. You’ll need to be as accurate as possible, especially with small dogs. They can be sensitive to the effects.

Liquid Benadryl can be given to the dog directly with a dropper. Place the dropper in his mouth and shoot the medicine down his throat. It’s not pleasant, but it also won’t hurt the dog. Some dogs tolerate taking medicine this way just fine.

Other dogs prefer to eat tablets hidden in food. Wet food often works best. It hides the medicine from view and masks the taste.  

Benadryl should be given with a small amount of food to help prevent stomach upset.

How to Use Benadryl Safely

Check the ingredients carefully. You want pure diphenhydramine. Some brands add additional medications such as acetaminophen or pseudoephedrine. While those ingredients are perfectly fine for a person, they’re usually toxic to dogs. Also, avoid formulas with alcohol.

Many pet parents choose a children’s brand of diphenhydramine with the assumption it’s gentler than medicine for adults. However, children’s formulas often contain artificial sweeteners or flavors which can cause digestion problems in dogs.

You want 100% pure diphenhydramine. It’s also called “generic diphenhydramine” or “generic Benadryl.” It contains no additional medicines or other ingredients. Most brand-name Benadryl sold in the U.S. is pure diphenhydramine, but you’ll want to check the label to be sure.  

You can find diphenhydramine marketed specifically for use by dogs. Anything called “Benadryl for dogs” is the same pure diphenhydramine for people. Feel free to shop around for the lowest price. Don’t pay extra for pure diphenhydramine just because it’s marketed to pets. You’re not getting anything special.  

Avoiding Potential Medical Problems

Even pure diphenhydramine can potentially cause problems. Avoid giving dogs diphenhydramine if your dog has any of the following conditions:

  • Glaucoma
  • High blood pressure
  • Cardiovascular disease

Also, make sure the diphenhydramine won’t interfere with any other medications your dog may be taking. Contact your vet before giving your dog Benadryl for the first time.

Benadryl is generally safe to administer to dogs:

  • Who currently are taking no other medications
  • With no existing medical issues
  • Suffering from a mild to moderate allergic reaction

Diphenhydramine is not an effective treatment for an acute allergic reaction. If your dog is experiencing facial swelling, difficulty breathing or other problems which are rapidly developing, skip oral medication. Instead, take your dog to the vet for professional treatment.

When Should I Give My Dog Benadryl for Non-Allergy Related Reasons?

Benadryl helps with more than just allergies. As long as you follow the dosing guidelines and other care instructions, it’s safe to give your dog Benadryl for the following reasons:

Combating Motion Sickness

Benadryl often helps prevent vomiting, queasiness and other issues caused by movement in a car or plane.

Mild Sedation

Many dogs feel sleepy after taking Benadryl. It’s useful for keeping dogs calm in stressful situations such as the Fourth of July.

Does Benadryl Have Side Effects?

It can. For the most part, side effects are mild and temporary. They’re also typically similar to side effects experienced by people. Common side effects include:


Benadryl makes dogs and people tired. Don’t be surprised if your dog goes to sleep within about 45 minutes after dosing. Even if he doesn’t sleep, his energy levels will likely be low while the Benadryl is in his system.

Along with drowsiness, another related symptom is drooling. While excessive drooling can look alarming, it usually goes away after a few hours.   


Some dogs have an opposite reaction to Benadryl. Instead of slowing down, they speed up. Benadryl can sometimes make dogs race around, bark and generally act excited.   

As with drowsiness, excitability is often temporary. However, you’ll want to make sure the dog doesn’t put himself at risk for any movement injuries like a twisted ankle. Also, make sure his heart rate or breathing doesn’t become too rapid.

What is a Benadryl Overdose?

Generally, Benadryl is safe when given in the correct dosage. However, accidental overdose is always a possibility.

The most common cause of an overdose is when a dog gets into a box or bottle on his own. Be sure and keep all medications stored safely in a drawer or other closed area. Dogs are especially attracted to the sweet taste of liquid Benadryl, although pills should also be kept secure.

Even administering the correct dose can potentially cause an overdose. Like people, some dogs are simply more sensitive to medications than others. Generally, you want to err on the side of lower doses when giving your dog Benadryl for the first few times.

Symptoms of a Benadryl overdose can include any or all of the following:

Extreme drowsiness. General tiredness and a desire to take a nap are normal side effects. But if your dog seems too tired to function properly, he might be overdosing.

Agitation. Benadryl can make dogs feel anxious and fearful. They might pace around the house or hide under the bed. Anxious dogs are more likely to bare their teeth and act aggressively. Speak to your dog in soft, reassuring tones and give him plenty of space.

Physical symptoms. Many overdose symptoms are easy to see. Watch for muscle tremors, breathing difficulties (either too fast or too slow), shakiness and excessive panting. Your dog’s body temperature and blood pressure might also rise.

If you suspect your dog is overdosing on Benadryl, take him to the vet immediately. The earlier the treatment begins, the greater his chances of recovery.

Final Thoughts

Before giving Benadryl, check with your vet if your dog has any existing medical issues or is taking any prescription medications. Also, check with your vet before giving Benadryl to your dog for the first time.

Make sure you only use pure diphenhydramine with no alcohol, acetaminophen or pseudoephedrine. Give your dog 1 mg of medicine per pound in weight.

Benadryl is safe and effective when properly administered to healthy dogs. Allergies are no fun – for people or pets! Fortunately, relief is available.