Benadryl For Dogs – Is it Safe?

Is your dog itchy or does he suffer from motion sickness?

If the answer is “Yes”, then it may have occurred to you to try Benadryl in order to settle his symptoms.

Benadryl is a popular antihistamine for people, which is widely available without a prescription.

However, when giving dogs Benadryl you need to be aware of a few simple does and don’ts in order to avoid some potentially dangerous complications.

1. What is Benadryl?

Let’s start at the beginning by looking at what Benadryl is and when you can consider Benadryl for dogs.

Benadryl is the trading name for a group of products that contain antihistamines.

And this is where the first warning pops up.

For many years the Benadryl brand contained the active ingredient diphenhydramine.

This drug is safe for the majority of dogs (although there are some dogs who shouldn’t take it) and has some interesting properties such as alleviating itchiness, reducing motion sickness, and soothing coughs.

However, recently new drugs have crept into the Benadryl product range, for example, cetirizine (an antihistamine), acrivastine, and pseudoephedrine (a decongestant).

Whilst cetirizine is safe for most dogs, it is purely an anti-allergy product and has no effect on coughs or motion sickness.

Also, there is not enough data to know if acrivastine is safe for dogs and so is best avoided.

But most important of all is to know that pseudoephedrine is potentially toxic to dogs.

This means that a Benadryl product that says “decongestant” on the label is likely to contain pseudoephedrine and is therefore NOT safe for dogs.

Thus when wondering “Is Benadryl safe for dogs?” – The answer, yes and no, it depends on the active ingredients.

2. Follow the rules

When you pick up a Benadryl packet, always read the active ingredients!

• Greenlight to go ahead:

• Diphenhydramine
• Cetirizine

• Red light to stop:

• Pseudoephedrine
• Acrivastine

Of course, always check with your veterinarian first before giving any new medication, because safe for a healthy dog, may not mean safe for a dog with an underlying health problem or that is already on medication.

For example, do NOT give any Benadryl product if your dog has the following:

• High blood pressure
• Glaucoma

• Urinary problems (including incontinence)
• Overactive thyroid glands

• Take an MAO inhibitor medication such as isocarboxazid, phenelzine, or tranylcypromine

All of the above can have potentially serious interactions with Benadryl products or other antihistamines and mixing the two is not advisable.

3. What is an Antihistamine and How Do They Work?

Diphenhydramine and cetirizine both belong to a group of drugs called antihistamines.

They were developed to alleviate the signs associated with allergies in people such as hay fever, with its associated sneezing, hot itchy eyes, and a runny nose.

It just so happens that some antihistamines have other actions such as relieving nausea associated with travel sickness and reducing the urge to cough.

Unfortunately in dogs, the effect of antihistamines can be disappointing.

They can work well in some dogs, but in others, they either have a reduced effect or are of no benefit at all.

Sadly, it is impossible to predict if Benadryl will help your dog and the only way to know is to try it and see. (Provided it is safe to do so).

Antihistamines work by counteracting a substance in the body called histamine.

This is released from mast cells as part of the body’s immune response when it detects foreign substances called allergens.

You will be most familiar with allergens such as the pollens which cause hay fever in humans.

In some cases, the body gets carried away and produces an excessive amount of histamine which then leads to inflammation, irritation, and itchiness.

By canceling out the extra histamine, antihistamines calm this allergic reaction.

Dogs also experience allergic reactions to substances in the environment, and this condition is known as atopy.

Rather than sore eyes and a runny nose, this more typically shows itself as itchy skin, with the dog obsessively licking or chewing his feet.

However, as already mentioned, the response to antihistamines can be disappointing in some dogs and it’s a case of trying it to see what happens.

4. Dogs and Benadryl

So when might Benadryl be useful to give to your dog?

Consider using Benadryl product containing diphenhydramine in the following circumstances:

• The dog is otherwise healthy and not on other medications
• Has an allergic itch

• Has a cough
• Suffers from motion sickness

Consider using a Benadryl product containing cetirizine in the following circumstances:

• The dog is otherwise healthy and not on other medications
• Has an allergic itch

5. What is the Benadryl Dosage for Dogs?

First, take a look at the Benadryl packaging to discover what the active ingredient is and confirm there is no pseudoephedrine or acrivastine present!

A) Active ingredient: Cetirizine

This is commonly found in the ‘one a day’ or ’24 hour action’ allergy relief formulations.

Bear in mind this is purely for allergy symptoms, and will not benefit the coughing dog or one that suffers from motion sickness.

The Benadryl dosage dogs take is 1 – 2 mg/kg body weight once a day.

This means a 10 kg dog needs 10mg once a day, which is equivalent to a single Benadryl Allergy Liquid Release capsule.

This is given with our without food but it’s best to wash it down with a drink of water.

B) Active ingredient: Diphenhydramine

The Benadryl dose for dogs that are itchy is 1 – 2 mg/kg body weight, two or three times daily.

This is equivalent to a 10kg dog taking half a Benadryl Allergy 25 mg tablet.

Usually, a maximum dose of 25 – 50mg is given, even to giant dogs.

When working out how much Benadryl for a dog with motion sickness or a cough, it is slightly higher at 2 – 4 mg/kg body weight, given two or three times daily.

This works out at about one to one-and-a-half Benadryl Allergy 25 mg tablets for a 10 kg dog, with a ceiling dose of 50mg for even the largest dog.

Be aware the diphenhydramine does have a sedative effect on some dogs.

This may be a hidden blessing for the dog with kennel cough that can’t sleep at night.

However, if you are using Benadryl to relieve travel sickness, it might be not such a good choice if you want the dog to be lively at the other end of the journey.

For example, if your dog gets sick on the car ride to the dog park, then giving Benadryl may make him too sleepy to play when you get there.

If however you are moving house and it would be helpful that Fido isn’t bouncing off the walls when you arrive at your new pad, then being sleepy can be a bonus.

Bottom Line

Just to further complicate things, you will find the active ingredients in Benadryl products vary between countries.

Whilst the US Benadryl contains mainly diphenhydramine, this is not the case in the UK.

If you happen to have a product obtained from the UK, check the packaging carefully since most contain acrivastine.

At the present time there is little data about this newer drug, acrivastine, and how it affects dogs.

With this in mind, it is not safe to give to dogs.

For those living in the UK, alternative products containing diphenhydramine include Nytol, Sleep-eze, and Siladryl (always check the label before administering).

Indeed, it’s important to be aware that none of the products mentioned in this article are licensed for use in dogs by the FDA.

As such you are therefore using them ‘off label’ and at your own risk.

Always be cautious when giving any medication to a pet and it’s always best to check in with your vet first to check it is safe to do so.

Best of luck and here’s hoping for a relaxed, itch-free pet this summer pollen season! Read our comprehensive guide on https://dogstruggles.com/medication/.

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Sarah Robinson

Dr Sarah Robinson attended veterinary school at Oklahoma State University receiving a D.V.M. in 2008. Sarah’s longtime interest is to help people to better communicate with their pet companions, and in doing so, to help them to strengthen their relationships with their dogs and cats. Sarah has published numerous articles on canine feeding in pet related magazines, veterinary journals and leading natural health web sites.