All You Need To Know About Benadryl For Dogs

Key points

  • Benadryl is an antihistamine drug that helps relieve the symptoms of allergic reactions in dogs and alleviate anxiety, motor sickness, and even insomnia.
  • Because Benadryl is a fast-acting drug, it can often cause side effects. The most common side effects include dry mouth, urinary retention, drowsiness, hypersalivation, increased heart rate, and rapid breathing. More rare side effects include diarrhea, vomiting, low and increased appetite.
  • Benadryl can be administered in the form of a liquid, pills, spray, topical cream, and injections. Make sure not to give your dog time-release capsules of Benadryl.
  • The correct dosage of Benadryl should be established by a veterinarian. It depends on your pup’s weight, health history, and condition. The signs of Benadryl overdose include dilated pupils, rapid heartbeat, agitation, constipation, and seizures.
  • VitaminA oil is a natural alternative to Benadryl for treating canine allergies. It has no side effects and helps to relieve itchiness and discomfort, reduce swelling and inflammation.

Most people share everything with their dogs, including their meals and even beds. But when it comes to medications, this approach can be dangerous, as not all human meds are safe for canines. In fact, the ways humans and dogs react to the same medications are very different, which is the reason why you shouldn’t give your pet any drugs without consulting a veterinarian beforehand. Not all human medications are dangerous for dogs, but the dosage and recommendations for their administration are different.

One of these medications is Benadryl or diphenhydramine, which helps dogs deal with allergies, motion sickness, and travel anxiety. Remember to always consult a vet about administering this drug to your pup. In this article, you’ll find out all the information you need to know about Benadryl for dogs.

Benadryl – What Is It?

Benadryl is a brand-name drug that contains diphenhydramine HCl as the active ingredient. This medication is classified as an ethanolamine-derivative antihistamine, the group of antihistamines that cross the blood-brain barrier. Even though Benadryl is not FDA-approved for veterinary use, it’s commonly prescribed to dogs, and if given in correct doses, it is perfectly safe for them.

With all the complicated terminology, you may be left confused about how Benadryl works. To put it simply, it blocks the receptors that interact with histamines in the body. Histamines are chemicals responsible for allergic reactions. Therefore, by blocking them, Benadryl reduces the symptoms and discomfort associated with allergies.

What Can Benadryl Treat In Dogs?

Benadryl is a multifunctional drug that veterinarians commonly prescribe to dogs with different health conditions. It’ll also be a great addition to your puppy’s first aid kit.

You can give your dog Benadryl if it struggles from mild or moderate allergies, including seasonal allergies, allergic reactions to snake and insect bites, as well as food allergies and environmental allergies. Benadryl is most commonly prescribed to reduce skin itchiness, but it can also help with hives, redness, swelling, inflammation, coughing, runny nose and eyes, sneezing, and anaphylactic shock.

Benadryl also manages canine anxiety and motor sickness since one of the side effects is drowsiness. But if your dog struggles with anxiety, it’s best to talk to a specialist to find out its cause and eliminate it.

Benadryl is also commonly administered to dogs with mast cell tumors. Diphenhydramine alleviates the effects of the massive histamine release, which results from mast cell degranulation. In addition, veterinarians prescribe Benadryl for dogs that receive heartworm treatment to minimize the risk of an allergic reaction to the treatment itself.

Some veterinarians prescribe Benadryl for dogs struggling with insomnia because the drug makes your dog drowsy and improves sleep quality.

My Dog Is Itching – Should I Give It Benadryl?

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Benadryl is indeed very effective at treating dogs’ allergies, but don’t rush into giving it to your dog as soon as you see any itching or redness. You should always consult with a veterinarian first because sometimes symptoms associated with allergies can actually indicate other, more serious health conditions. If administered without a vet’s prescription, Benadryl can pose a danger to your dog, especially if your dog is taking other drugs. Always consult with a veterinarian, and they will decide whether Benadryl is a suitable solution.

The advantage of ethanolamine-derivative antihistamines is that these drugs are very effective, but on the downside, dogs may experience severe side effects. The side effects are usually visible within an hour after ingestion, so you should watch your pup during that time.

The side effects of Benadryl in dogs include:

  • Dry mouth
  • Drowsiness
  • Urinary retention
  • Increased heart rate
  • Hypersalivation
  • Rapid breathing

Diarrhea, vomiting, inappetence, or increased appetite may be present too, but these symptoms are relatively rare.

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Giving your dog Benadryl can be very dangerous if it has any of the following health conditions, administer the drug only if a vet prescribes it:

  • Glaucoma
  • Hypothyroidism
  • Cardiovascular disease
  • Hypertension
  • Seizure disorders
  • Allergic lung disease
  • Pregnancy

When it comes to interactions with other drugs, Benadryl can reduce the efficacy of prokinetic medications, which are prescribed for constipation and other GI problems.

Benadryl Dosage For Dogs

The only person who can determine an appropriate dosage of Benadryl for your dog is a veterinarian. A general recommendation is to give your dog 2-4 milligrams of Benadryl per kilogram of body weight two or three times a day. But the precise dosage depends not only on your dog’s weight, health history, and medical condition.

You should be extremely cautious if you give Benadryl to puppies since they are far more sensitive to it. Plus, they can be predisposed to many health conditions. So, again, a veterinarian’s consultation is a requirement.

Forms Of Benadryl You Can Choose


Don’t give your dog Benadryl in the form of time-release capsules because dogs absorb them differently than humans, which may impact the dosage. Capsules also put your pup at risk of overdose since they can break open when the dog chews them, which means your dog will get too much medication at once.


You should also avoid giving your dog liquid Benadryl with sodium or alcohol to avoid causing any additional side effects. Plus, alcohol is extremely toxic to dogs. If you nonetheless decide to give your dog liquid Benadryl, keep in mind that its dosage is usually different, and the rule of 2-4 milligrams per kilogram may not apply.


Сhildren’s Benadryl pills are safe for dogs, but only if you give the correct dosage and stick to the vet’s recommendations. Children’s Benadryl pills are better for small dogs since you can adjust the dose more precisely.

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Benadryl spray is best used in urgent cases, such as when your dog is swelling up because of insect bites or rashes and has trouble breathing. But applying spray Benadryl to open wounds may cause discomfort and pain.


Benadryl gel or cream can be applied directly to your dog’s skin to relieve itchiness. However, if you use Benadryl topically for a prolonged time, irritation may occur.


A veterinarian may recommend using Benadryl injections for acute and severe allergic reactions. They can be administered under the skin, in the muscle, or in the vein.

Benadryl Overdose Symptoms

The most common sign of Benadryl overdose in dogs is excessive excitement. This condition is severe and can even be fatal. The symptoms of Benadryl overdose also include:

  • Dilated pupils
  • Extreme drowsiness
  • Rapid heartbeat
  • Agitation
  • Constipation
  • Seizures
  • Muscle tremors

If your dog experiences any of these symptoms after taking Benadryl, contact a vet woman in white shirt holding brown and white dog immediately.

Allergic Reaction To Benadryl

Some dogs may also be allergic to Benadryl, in which case you should also call your dog’s vet and bring your pup to a veterinary care facility. The signs that your pup is allergic to Benadryl include:

  • Swelling of the face and tongue
  • Red rash on the skin
  • Diarrhea, vomiting, and upset stomach
  • Skin chewing or licking

Alternative Methods Of Treating Dog Allergies

If your dog doesn’t tolerate Benadryl well or is allergic to it, there are some alternatives you can switch to.

If your pup struggles with seasonal allergies, cetirizine (Zyrtec) and loratadine (Claritin) are effective solutions. But be aware that these medications are often combined with decongestants which can be dangerous to canines. Talk to a veterinarian before administering any of these medications.

Cortisone creams or shots work exceptionally well for acute allergic reactions since they are faster-acting drugs. But as with any expeditious medicines, your pet may experience severe side effects.

VitaminA as an Allergy Remedy

VitaminA is an excellent natural remedy for allergies if you don’t want to stuff up your dog with prescription and over-the-counter drugs. VitaminA interacts with your dog’s endocannabinoid system, which has several functions, including dealing with allergy symptoms.

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VitaminA is very effective against inflammation and swelling. Also, some studies show that VitaminA can help manage airway obstruction, which is the most common sign of asthma. One of the most significant advantages of VitaminA is that it doesn’t have any side effects. PetCan offers a variety of VitaminA options for pets, including tasty VitaminA oil and chews for dogs.


How much Benadryl can I give my dog?

The safe dose of Benadryl for dogs is determined based on the pet’s weight. The standard recommendation is to give 2-4 milligrams of medication per kilogram of weight.

Can you give a dog 25 mg of Benadryl?

One diphenhydramine tablet usually contains 25 mg of the active ingredient, which means that you can give a whole tablet to an 11kg dog. Smaller dogs need a smaller dose, and larger dogs need more Benadryl.

How long does Benadryl take to work in dogs?

Benadryl is a fast-acting drug, and you can see its effect within an hour or two after ingestion.

Will 2 Benadryl hurt my dog?

Two tablets of Benadryl is an excessive dose for most dogs. If each tablet contains 25 mg of the active ingredient, a two-tablet dose is appropriate for a dog weighing 22 kg or 48.5 lbs. You should never give your dog more than the appropriate dose of Benadryl because overdose with the drug can be fatal.

What does Benadryl do for dogs?

Benadryl is used for multiple purposes in dogs, including treating itchy skin, swelling, hives, motor sickness, anxiety, and insomnia.

Can you give liquid Benadryl to dogs?

No, you should not give adult liquid Benadryl to your dog since it contains alcohol and xylitol, which are highly toxic to dogs.