Benadryl For Dogs – A Complete Guide To Giving Benadryl To Your Dog

Benadryl For Dogs

Benadryl is an over the counter antihistamine for humans. It is used to treat the symptoms of allergies, such as itchiness, sore red eyes and runny noses. Benadryl for dogs is the use of human Benadryl products to relieve the same symptoms in our canine companions. veterinarians often suggest using Benedryl for dogs with allergies, but it is not FDA approved.


What Does Benadryl For Dogs Treat?

Benadryl for dog allergies is the most common use of this drug. However, there are a few more ways in which Benadryl may be used by pet owners. These include treatment of the symptoms of:

  • Hives
  • Itching
  • Runny eyes
  • Runny nose
  • Stress
  • Anxiety
  • Travel sickness

The science behind Benadryl for dogs

Benadryl is the brand name for a product containing diphenhydramine, an antihistamine. The brand Benadryl has been around since 1946. Studies have proven its efficacy in dogs as far back as 1947. Though, it is difficult to pin down exactly whose idea it was to administer it to a dog!

The most important thing for you to know are the active ingredients. Depending on what part of the world you are in the active ingredient may differ. In the US & Canada as well as Australia and New Zealand the active ingredient is diphenhydramine. Whereas, in the UK, the active compound is either acrivastine or cetirizine.

Whatever the compound, they largely work in the same way. When you have an allergic reaction, your body processes a substance called histamine. This causes the symptoms of the allergy, like inflammation and runny eyes or nose. Antihistamines block the uptake of histamine, causing the symptoms to be reduced or stop altogether.

Is Benadryl safe for dogs?

Benadryl given in the right dose should not cause an otherwise healthy dog any serious problems. However, if your dog has an existing medical condition, it can be dangerous. For example, you should not give Benadryl to a dog already suffering from glaucoma, high pressure, prostatic disease, hyperthyroidism or cardiovascular disease. As with any other medication, it’s always good to have a chat with your veterinarian before you give your dog Benadryl.

Dog Benadryl toxicity

The lethal dose (LD50) for diphenhydramine in dogs ranges between 5 to 6 mg per pound of bodyweight by IV administration. It is therefore possible for a dog to overdose and die from overconsumption of Benadryl. As few as 4 tablets of 25mg taken orally can be a lethal dose, though it may take many more in some cases. The risk is not worth taking. Keep all medicines out of reach of curious snouts.

Using Benadryl for dogs safely

How much Benadryl is safe for a dog depends upon the dog’s weight and any pre-existing medical conditions. For a dog in otherwise good health we calculate the dosage by weight.

1mg per pound in weight of Benadryl is the formula that is normally used. Benadryl usually comes in 25mg tablets, but you must check the packet carefully. Again, we must stress that the best thing you can do is to consult your vet before administering any medicine.

Can you give human Benadryl to dogs?

While Benadryl is not sanctioned by the FDA for use in dogs, the literary and veterinary opinion suggests that it is safe to do so in some cases. However, it is not wise to give your dog any medication, particularly human medication without consulting with your vet.

Some varieties of Benadryl will contain other ingredients such as painkillers, expectorants (to make you cough) or decongestants, which are not appropriate for animal use. Children’s Benadryl can contain sodium too, which is not advised either.

Warning: Liquid Benadryl

You must not give your dog adult Liquid Benadryl. You can however give your dog Children’s Liquid Benadryl if your vet confirms that it is appropriate for us on them. Liquid Children’s Benadryl usually has 12.5mg diphenhydramine in every 5ml. This means that you can give 0.4ml of liquid children’s Benadryl per 1lb body weight. So a 35lb dog would have a 14ml dose, for example.

Warning: UK Readers

There are forms of Benadryl in the UK that contain cetirizine. These are best avoided as they won’t provide the same medical solution as diphenhydramine.

Benadryl for dogs

Severe Allergic Reactions

If you think that your dog is having a severe allergic reaction, do not give him Benadryl. Don’t delay in rushing him to the vets. Severe signs of allergy include trouble breathing, potentially with swelling of the face or neck. This can be potentially life threatening and requires immediate medical treatment from a qualified veterinarian.

If they think that your allergic dog would benefit from Benadryl then they will help you by calculating the correct dosage.

Using Benadryl to treat dog itching

Itching is one of the most common signs of an allergic reaction. Benadryl, like other antihistamines excel in alleviating the discomfort of itchy skin in humans and dogs alike.

Itching is symptomatic of some kind of skin irritation. This is commonly caused by an allergic reaction to contact with a foreign body or allergen. We all know it can be difficult to resist itching a mosquito bite or a nettle sting or any number of itchy intrusions. Unfortunately, dogs suffer from the same kinds of itchiness.

It might not seem like a major problem. However if the itchiness persists, it can lead to your dog causing much more damage to himself by scratching. It may even lead to an open wound and, in turn, an infection.

Benadryl for itching in dogs

Benadryl is an effective antihistamine in dogs. Therefore, in cases where itching is caused by the release of histamine, it should prove to be somewhat useful. If your dog’s itching persists, it’s likely that his itching is not the result of a reaction that induced a histamine response. In that case, consult your vet and she will help you deduce what the problem is.

Benadryl dosages for dogs with itchiness

Your vet might prescribe 1mg of Benadryl for every pound your dog weighs. Benadryl can be given at that dose 2 – 3 times a day. So, every 8 – 12 hours.

Using Benadryl to treat dog anxiety

Benadryl for dogs anxiety is occasionally recommended as a temporary measure by veterinarians, as it can produce mildly sedative results. However using Benadryl to calm dogs is not something that is a good idea on a regular basis, or as an alternative to behavioral training exercises and socialization.

Side effects of Benadryl for dogs

Remember, all remedies and medicines that have a clinical effect will also have potential side effects. Benadryl is no different. Benadryl can have side effects, most of which are mild.

The main ingredient diphenhydramine has been known to cause drowsiness and dizziness. It can also cause stomach problems such as constipation or diarrhoea. If your dog seems to be showing signs of an upset stomach, then speak to your vet before continuing with the next dose.

There are some rare severe side effects of Benadryl for dogs, which is why it is a good idea to speak with them before you use it.

Benadryl benefits for dogs

Benadryl may be a useful tool to have in your box. It can come in handy if your dog is experiencing itching. It may even be useful in a pinch when it comes to any anxious episodes he might have. However, it’s worth remembering that Benadryl is formulated for humans. As such, you need to exercise due diligence. Always read the label. Never give your dog any medication that has more than the active ingredient you require.

It’s much easier to give your vet a call before you administer any medication than it is to rush your sick pooch to the emergency room. So, while Benadryl has its uses, there are plenty of medicine on the market that are specifically for dogs. They might be a better bet.

The Labrador Handbook by Pippa Mattinson(paid link)

Giving Benadryl to your dog

If you have checked the correct dose of Benadryl, spoken to your vet and are confident that this is the right product for your dog, then you will need to think about how to give your dog a Benadryl tablet.

One way is to wrap the tablet in some tasty meat or cheese, or pop it inside a treat pouch if you have one handy. It’s a good idea to have a second lump of meat of cheese (without a tablet in it) clearly ready and obvious to your dog when giving him the treat containing his medicine. This makes him more eager to swallow the concealed tablet, as he will be keen to get the second treat that he can see waiting

Monitor your dog for any side effects. And contact your vet if you have any concerns

The Labrador Site Founder

Pippa Mattinson is the best selling author of The Happy Puppy Handbook, the Labrador Handbook, Choosing The Perfect Puppy, and Total Recall.

She is also the founder of the Gundog Trust and the Dogsnet Online Training Program 

Pippa's online training courses were launched in 2019 and you can find the latest course dates on the Dogsnet website


  1. I have a rottweiler who has very itchy skin and I’ve no idea what is causing it .very flaky skin around his bum and belly and also tale.

  2. My 11 year old Labrador female has been taking the pink generic Benadryl tablets twice a day since she was 3 years old at my vet’s direction. She would get ear infections from constantly getting her ears wet by dipping her whole head in her drinking bowl. She also has a problem with seasonal allergies and will develop red, itchy eyes. The Benadryl has taken care of those issues, and she’s had no side effects. I also give it to my 3 year old Lab mix twice a day. My vet told me that it doesn’t affect dogs like people; they don’t get sleepy from it.

  3. Thanks for article but all the Benadryl I’ve seen for sale contain ingredients other than diphenhydramine. Where in the uk can I buy the one recommended?