Benadryl that can be given to a dog

Benadryl For Dogs – All You Need To Know

Its a beautiful weekend and finally, you have decided to clean the eavestrough, a chore that you’ve been putting off for ages. So, you ascend the rickety ladder and are scrubbing away removing leaves and debris, when suddenly, you poke your brush into a hornet’s nest.

Within seconds, an entire squadron of the angry insects swarm over you and your little furry friend, who was keeping you company at the base of the ladder.

After a few grueling and painful hours, you have taken a gulp or two of Benadryl to ease the hives that have mushroomed all over your arms. But your dog also has taken a few stings and seems a bit under the weather.

The question is, can you give him Benadryl, a medication that is clearly meant for human use?

Situations like these pop up every now and then all around the world, where a pet owner is confused about giving a human medication to their dogs. Believe it or not, Benadryl seems to be the most common one.

If you are one of them, then here’s some low down on using Benadryl for dogs.

What is Benadryl?

Benadryl is a brand name for an over-the-counter antihistamine medication that is commonly used for relieving allergy symptoms in humans. In technical terms, it blocks the H-1 receptors on smooth muscle and blood vessels. In simpler terms, whenever the body suspects that it’s invaded by a foreign entity, it triggers the release of histamine, a chemical that causes allergy symptoms like runny nose and watery eyes. Benadryl prevents the uptake of histamine in the body and helps reduce these symptoms.

The active ingredient in Benadryl is usually Diphenhydramine, whereas in some countries like UK, the active ingredient is Cetirizine instead of Diphenhydramine. Most drugstores may also store other versions of Benadryl which contain other ingredients like acetaminophen or pseudoephedrine. 100% pure Diphenhydramine and Cetirizine is generally considered to be safe for dogs in small, controlled doses. However, if there are added ingredients like acetaminophen, then it may be toxic for dogs.

So, as a rule of thumb, you should always consult your vet before giving your dog Benadryl. In all probability, it will do him some good and ease him down. But better be cautious than sorry.

Sick Jack Russell resting in bed

When can Benadryl be given to a dog?

There are many situations in which giving Benadryl may be useful for your dog. Here are some of them.

  • Insect stings
  • Allergic reactions to vaccine
  • Itchy and reddened skin
  • Stuffy and runny nose
  • Asthma
  • Reactions caused due to blood transfusions
  • Inflammation caused due to mast cell tumors
  • Nausea

Other than these, your vet may also recommend giving your dog Benadryl, if the situation demands it.

How soon does Benadryl start working?

Benadryl is rapidly absorbed in the body and it should start to work in as less as 30 minutes from the time of administration. So, if you are giving your dog Benadryl to prevent motion sickness during travel, then you should give it at least 30 minutes before you commence the journey.

Is Benadryl safe for dogs?

Yes. As we said earlier, it is generally well tolerated in dogs. However, here are a few caveats that you need to be aware of:

  • It may be unsafe for puppies: Puppies can get really restless if they don’t feel well and you may be tempted to give them some Benadryl to help them rest. But, you must be careful and always speak to your vet before giving it. Puppies, like human babies, have very specific medication guidelines and Benadryl may not be safe for them.
  • Combination drugs: There are many versions of Benadryl available over-the-counter. Some have added ingredients like fever reducers and decongestants added to them. If you are buying Benadryl for your dogs from a drugstore, then ensure that you read the product label information to rule out the presence of unwanted ingredients.
  • Alcohol: In addition to these drugs, some versions of Benadryl contains alcohol, sodium or added sweeteners which are not recommended for children and for dogs.
  • Know the contraindications: The use of Benadryl is considered unsafe if your dog has prostatic disease, cardiovascular disease or glaucoma.

What is the correct Benadryl dosage for dogs?

Well, that depends on the dog breed and the size of the dog.

The usual recommended Benadryl dosage for dogs is 1 mg/lb taken thrice a day, or once every 8 hours. However, in some cases, this dosage may be doubled to help alleviate the symptoms. This recommended dosage is only applicable for Benadryl formulations that contain 100% diphenhydramine though.

As always, it is in your best interest to speak to your vet before administering a dose of Benadryl. Your vet will consider the dog’s medical history, breed, the symptoms and the cause of the condition before suggesting the right dosage.

For example, in small dogs, vets usually recommend using the children’s formula of Benadryl.

Woman holding dachshund dog at the vet clinic

Are there any side effects?

Diphenhydramine is usually a harmless medication with very mild side effects, if any. The most common side effect is drowsiness, because it inhibits acetylcholine receptors in the body. This is the reason why it is also sold as a sleeping aid and may also be prescribed to help calm your dog down.

Besides this, some of the common but mild side effects that your dog may experience are:

In rare cases, some serious side effects like these may also occur:

  • Rapid heartbeat
  • Drooling
  • Fast breathing
  • Vomiting and diarrhea
  • Severe allergic reaction with swollen face

Side effects are usually seen within 1 hour of administering the dose. If you feel that the dog is experiencing a severe side effect, then contact your veterinarian immediately and seek emergency medical care.


Most pet owners are diligent about administering only the exact recommended dose to their pets. But in some cases, an accidental overdose can occur, causing severe symptoms.

  • Abnormal behavior
  • Unable to breathe
  • Fever
  • Anxiety
  • Agitation
  • Sudden tremors
  • High blood pressure
  • Seizures

A Benadryl overdose can be potentially fatal and demands emergency veterinary care. If you suspect that your dog may have ingested more Benadryl than what’s recommended, contact your veterinarian immediately.

Closing note

This may sound like a broken record. But contacting a vet takes the guesswork out of pet care. Benadryl and some other human medications are generally safe for use in dogs. In many situations, they may even be a lifesaver. But, it is equally important to know that you are giving them the right drug in the right dosage. So, never play pharmacist to pets and always speak to the expert first.