How Much Benadryl Can I Give My Dog?

Written by: Milica Brzakovic
Is it safe and what are the appropriate amounts? These are questions you should ask yourself with every medication. This article focuses on Benadryl.

Giving medication to your dog is inevitable in some cases.

Therefore, it’s vital that you inform yourself and that you’re sure of what’s safe to use and how much.

So, what’s the case with Benadryl? Can it be given to dogs?

Humans and dogs can react very differently both to food and medications. However, there are some food and medication both of you can have safely. But, if you don’t want your pet to consume something that’s bad for dogs, you should always inform yourself before you give something new to your pet. Don’t just assume that a medication that can help you will help your dog as well.

So, before we get into detail, let’s see what Benadryl is and why it’s used.

What Is Benadryl?

Benadryl is an over-the-counter antihistamine, whose main ingredient is diphenhydramine HCL. Remember that Benadryl is only the brand name, while the active ingredient is the above mentioned dipenhydramine. This is important to know as different brands have this active ingredient, only under a different name.

This medication is blocking the H-1 receptors on smooth muscle and blood vessels. The antihistamines in Benadryl can cross the blood-brain barrier which makes them very effective, but they’re also more risky when it comes to side effects.

Benadryl is mostly used to treat environmental allergies, allergic reactions to bites and stings and pre-treatment of vaccine reactions. Diphenhydramine relieves many allergy symptoms, such as sneezing and itching, which is why this medication is mostly used in these situations.

Can I Give My Dog Benadryl?

Yes, it’s usually safe to give Benadryl to your dog, even though it’s not yet FDA-approved. With approval from your vet and used correctly everything should be fine. You’ll get to the dosage as you scroll down, but first let’s see what Benedryl can help dogs with.

What Should Benadryl Be Used For?

In general, this is a good medication for dogs with rather mild allergies, such as skin allergies or season allergies. Just like with people, Benadryl is good for reducing the allergy symptoms in dogs.

To sum it up, here’s what Benadryl can help with:

  • Itchy and irritated skin
  • Nausea
  • Insect and flea bites
  • Bee stings
  • Reaction to vaccines
  • Hay fever, sneezing or coughing
  • Runny nose
  • Asthma
  • Mild allergies
  • Car sickness
  • Insomnia
  • Swelling and inflammation

When Shouldn’t You Give Benadryl?

Even though Benadryl is in general safe and helpful to dogs, there are still some cases where you should be careful with Benadryl-use. Here are a couple of things to think about:

  • Be careful with giving Benadryl to your puppy. That goes for all medication. Be sure to consult your vet before you give anything to your puppy, as they’re still not completely developed and therefore more sensitive.
  • Avoid liquid Benadryl. The liquid form contains a lot of alcohol that’s definitely not safe for dogs. If you must use liquid Benadryl, opt for children’s formula as they usually don’t contain alcohol.
  • Make sure that diphenhydramine is the only active ingredient. While that’s safe for dogs, many other cold ingredients are not – fever reducers for instance are not safe for dogs.
  • Don’t give Benadryl before you check with your vet what conditions this medication is contraindicated with. Glaucoma, cardiovascular disease, hyperthyroidism and prostatic disease are some conditions that usually don’t go well with Benadryl.
  • Avoid Benadryl formulas with sodium, as it could create problems for dogs who are taking medications for some conditions. Choosing a formula without Benadryl is probably the safest option.
  • If your dog is pregnant or nursing, ask your vet if Benadryl is safe for your dog as it’s usually not recommended for these dogs.
  • Don’t give more than the recommended dosage.

How Much Benadryl Should I Give?

It’s very important that you don’t exceed the dosage, as your dog might get overdosed otherwise. The dosage isn’t the same for all dogs and depends on the body weight. You should always consult with your vet who will determine the right dose.

The standard dosage for oral Benadryl is 1 mg per pound, given 2-3 times per day. The tablets are usually 25 mg, so they’re enough for a 25 pound dog. However, this isn’t the ultimate dosage and it can vary depending on your dog’s medical conditions.

Also, liquid Benadryl dosage is different than the dosage for pills, so if you have to use the liquid (children) form for some reason, always consult your vet before you start giving the medication.

Overdose Signs

If you exceed the recommended dosage, you could be dealing with overdose. Signs that are indiciatng an overdose are the following:

  • Hyper-excitability of the central nervous system
  • Agitation
  • Dilated pupils
  • Seizures
  • Rapid hearbeat
  • Constipation

Besides overdose, it’s possible for dogs to have allergic reactions to this medication. If you notice any of the mentioned signs or allergy symptoms, take your dog to the vet as soon as possible.

Benadryl Side Effects

Just like any other medication, Benadryl could cause certain side effects. It’s important that you’re aware of them before you start the treatment. The most common side effects are:

  • Dry mouth
  • Hypersalivation
  • Sedation
  • Disorientation
  • Increased heart rate
  • Fast breathing

Some rare side effects are:

Side effects usually appear rather fast after the medication intake, within an hour or so. Therefore, observe your dog for some time and make sure there are no side effects to Benadryl.

How Do I Give Benadryl?

1. Consult a vet
Number one is the most important tip and it can’t be stressed enough. Never start giving any medication, Benadryl included, on your own. And definitely don’t play with the dosage and try it out yourself. Instead, consult a vet who will determine the right amount and say if Benadryl is safe for your dog.

2. Start slowly
Don’t start with a full dose at once, as your dog could be showing side effects or an allergy reaction. Instead start off slowly with a small dose and wait for reactions.

3. Give with food
Giving medication with food or treats is a good way to avoid side effects, most importantly nausea.

4. Break the pill
Most dogs won’t be too happy about swallowing an entire pill. So what you can do is to break it and place it inside a piece of meat. Your dog won’t probably even notice anything.

5. Mix with wet food
If you’re giving Benadryl in a liquid gelcap, try to open it and mix it with some wet food. Just like in the previous case, your dog won’t taste the medication thanks to the food.


Benadryl is in general safe for dogs, which makes it appropriate both for us and our dogs. It can help relieve allergy symptoms, such as itchy skin and runny nose, but it can also be helpful in other situations, like with motion sickness and insect bites.

However, dogs with certain conditions shouldn’t take Benadryl as it can be counter-indicated with, for example, high blood pressure. You should also be careful if you have a puppy, as the rules aren’t the same for them. Because of these, and other situations, it’s vital that you consult your vet before giving any new medication.

The vet should also determine the dosage, which depends on the dog’s body weight. The general dose is 1 mg per pound, but that can also vary so don’t determine the dosage on your own. When you give Benadryl for the first time start slowly, with a smaller dose, and monitor for side effects or allergic reactions. If you notice anything, take your dog to the vet.

Remember – medications can help in many cases, but they can also do more harm than good if you don’t use it correctly. Consult with a specialist, follow the instructions and everything should be fine.