An in-depth look at Benadryl for dogs

Although the use of Benadryl for dogs hasn’t been officially approved by the FDA, it’s safe in most cases and can be used to treat anxiety and allergies. Make sure you read the label first to be certain that the Benadryl doesn’t contain pseudophedrine or acetaminophen.

Benadryl is an antihistamine medicine that’s available over the counter. We use it to treat allergy symptoms such as itchy eyes, runny noses and sneezing. It’s also used to treat coughs and to help with sleeping, among other things.

Dogs can also suffer from these things too, of course. And so what about Benadryl for dogs – can you give Benadryl to your dog, is it safe, and does it work?

Benadryl for dogs

You should always consult with your vet before giving your dog any medication. That said, Benadryl is an effective form of medication for dogs. Although the FDA have not officially approved the usage of Benadryl for dogs, in most cases it is quite safe and is often used for treating allergies and anxiety.

You should be aware that Benadryl is the brand name of a particular medication. The actual active ingredient is either diphenhydramine or cetirizine. Before giving any Benadryl to your dog, check the package. Make sure it lists one of these as the only active ingredient. Some formulations of Benadryl are mixed with other medications and can contain either pseudophedrine or acetaminophen. Both of these are poisonous to dogs, so it’s vital that you always check the label.

Diphenhydramine is usually used to treat allergies and to calm anxiety. It’s also used to treat motion sickness, and for insomnia. You can find it in branded medicines such as Nytol, which is a sleep aid, and Tylenol, which is used for pain relief and the treatment of allergies.

Cetirizine is often less effective than diphenhydramine for treating allergy symptoms. You can use it to treat itching though.

What can it be used to treat?

Vets will often prescribe Benadryl for dogs that suffer from allergies. A surprising number of dogs suffer from allergies to a wide range of things, such as:

  • Fleas.
  • Pollen.
  • Bee strings.
  • Insect bites.
  • Food (especially dairy and gluten).
  • Dust and dust mites.

Benadryl can help to relieve the symptoms of these allergies for some dogs. Typical symptoms of allergies include swelling and itchy, red or scabby skin, scratching, sneezing, vomiting and diarrhea. These symptoms will often show up within twenty minutes or so of a reaction.

Sometimes a dog will suffer more serious allergic reactions such as trouble with their breathing, facial swelling or seizures. If your dog suffers such a serious reaction you should consult your vet immediately, rather than trying to treat it with Benadryl.

Of course, in the case of a food allergy the only real way to treat it is to remove the root cause. But in the short term, Benadryl is a very effective treatment for the relief of symptoms of food allergies in dogs.

It’s also often used to treat dogs that suffer from travel sickness. If you transport your dog around in your car a lot and your dog suffers from motion sickness, then it can be a real lifesaver!

Another common use of Benadryl for dogs is as a sedative and to calm anxiety, particularly during noisy fireworks or thunderstorms.

It’s also frequently used to help nervous and anxious dogs to sleep at night.

Benadryl For Dogs

Something to keep in mind is that when giving dogs Benadryl over a long period, they can start to get used to it and this can make it less effective. If you are using it as a long term treatment, it’s worth talking to your vet. They may be able to prescribe or recommend other antihistamines that you can alternate with the Benadryl.

How to give it to your dog

You can purchase Benadryl in both liquid form and as tablets. The drawback of the liquid form is that it can contain high levels of alcohol. So it’s recommended that you use the tablet form.

If your dog refuses the tablet, you can try hiding it in your dog’s food, or you can cover it in peanut butter and then give it to your dog. If you’re having trouble, check out my guide on how to give a dog a pill.

If you have a young dog, then children’s Benadryl is recommended. This is the liquid form of Benadryl but doesn’t contain any alcohol. It’s the only liquid form that’s safe to give to your dog.

If you’re going to give your dog the liquid form, take care to convert the dosage correctly. A 5 ml dosage of Benadryl will be the equivalent of 12.5 mg of diphenhydramine.

The easiest way to give your dog the liquid form is to use a syringe to squirt it into their mouth. If you’re having trouble getting them to take it this way, try squirting water first to get your dog used to the sensation.

What dogs should not be given it?

It’s not recommended to give Benadryl to a pregnant dog, unless your vet advises you otherwise.

It’s also not recommended for dogs which suffer from some health conditions. Examples are:

  • Heart disease.
  • Kidney disease.
  • Lung disease.
  • Hyperthyroidism.
  • Glaucoma.
  • High blood pressure.
  • An enlarged prostate.

If you’re in any doubt at all about whether Benadryl is safe for your dog, then you should talk to your vet first.

How much Benadryl to give a dog

The correct Benadryl dosage for dogs varies according to the breed. It also depends on your dog’s medical history. This is why it’s important to consult with your vet first.


For diphenhydramine, the usual recommended dosage is 1 mg per pound of body weight, which equates to one 25 mg tablet per 25 pounds of weight.

So for example, if your dog weighs 10 pounds, the usual dosage would be 10 mg. That said, you can double the dosage if necessary.

It’s important that you weigh your dog properly before working out the Benadryl dosage. Don’t be tempted to just estimate your dog’s weight or you run the risk of giving them too much.

Benadryl takes about half an hour to work. So if you’re using it to calm your dog before a stressful event, you need to take this into consideration.


For Benadryl containing cetirizine, typical dosages are as follows:

  • Dogs between 0 – 15 lbs: 5 mg
  • Dogs between 16 – 39 lbs: 10 mg
  • Dogs 40 lbs and over: 15 mg

Dog Benadryl dosage chart

Below is a handy Benadryl dosage chart for dogs that you can use to work out how much Benadryl containing diphenhydramine to give to your dog. For each dosage, the recommended frequency is two or three times a day.

Dog WeightRecommended Dosage
5 pounds5 mg
10 pounds10 mg
12 pounds12 mg
15 pounds15 mg
18 pounds18 mg
20 pounds20 mg
25 pounds25 mg
30 pounds30 mg
40 pounds40 mg
50 pounds50 mg
75 pounds75 mg
100 pounds100 mg
125 pounds125 mg
150 pounds150 mg
175 pounds175 mg

How often to give it to your dog?

As per the Benadryl dosage chart above, you should administer the Benadryl 2 or 3 times a day, unless you’re using it to aid with your dog’s sleep, in which case only one dose may be needed.

You should wait for eight to twelve hours between doses.

If you’ve consulted with your vet first, as I recommend, then they will have prescribed a dosage and explained how often to give it to your dog. If your dog appears to be getting better, it’s important that you still continue to administer the correct dosage as prescribed.

Possible Benadryl side effects in dogs

It’s not uncommon for dogs to suffer some side effects when given Benadryl. These include:

  • Seeming spaced out and general sluggishness.
  • Dry mouth.
  • Reduced urination.
  • Lack of appetite.

Rarer but more serious side effects include:

  • Vomiting.
  • Diarrhea.
  • An allergic reaction.

If you your dog starts to show signs of serious side effects, you should consult your vet immediately.

Can a dog overdose on Benadryl?

Dogs can certainly overdose on Benadryl if they somehow take too much of it.

If your dog does overdose, it can be very serious and you should get them professional help as quickly as possible.

Some of the symptoms to look out for that indicate an overdose of Benadryl include:

  • Breathing problems.
  • Muscle spasms.
  • High heart rate.
  • Extreme tiredness.
  • High blood pressure.

If you think your dog has overdosed, take them to your vet immediately.


Benadryl is a safe treatment for dog allergies and other conditions such as anxiety, trouble sleeping, and motion sickness. Having said that, you should always consult with a vet first before giving your dog medication.

1 thought on “An in-depth look at Benadryl for dogs”

  1. Hi Gwen,

    In liquid form, 5ml of Benadryl is equivalent to 12.5mg of diphenhydramine.

    If your dog is 5 pounds, the correct dosage in mg is 5mg which is 2.5 times less than this.

    So the correct dosage in ml is 2ml (i.e. 2.5 times less than 5ml).


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