Benadryl for Dogs (Uses, Side Effects & Dosage)

Does your dog suffer from allergies? You may have heard Benadryl for dogs can help. Benadryl is an over-the-counter medication that’s widely available in drug stores. While it’s designed for human use, vets consider it safe for dogs—as long as it’s administered correctly.

Looking to learn whether Benadryl may be an effective treatment for your dog? Read on to learn all about Benadryl, what conditions it treats, its side effects, dosage, and more. Or, use the links below to jump ahead to a section of your choosing.

• What is Benadryl (Diphenhydramine)?
• What is Benadryl Used to Treat in Dogs?
• Side Effects of Benadryl in Dogs
• Benadryl Dosage: How Much Can You Give to a Dog?
• Alternatives to Benadryl for Dogs
• Is Benadryl Safe for Dogs: When to Speak to a Vet
• FAQS
• Final Notes

What is Benadryl (Diphenhydramine)?

Benadryl is a common brand name for the drug diphenhydramine, which is used to treat allergic reactions. When you or your dog come into contact with an allergen, your immune systems respond by producing a chemical known as histamine. Histamine causes the symptoms associated with allergic reactions, like sneezing, itching, hives, rashes, and more. Antihistamines like Benadryl reduce the effects of histamine, therefore minimizing allergic reaction symptoms.

While Benadryl can be safe for dogs and humans, it may not always be the best solution for your dog’s needs. If you believe that Benadryl can help address your dog’s health problems, it’s best to speak to a vet first about your dog’s issues, dosage, and more.

What is Benadryl Used to Treat in Dogs?

Benadryl is primarily used to treat allergies in dogs. It can address heightened levels of histamine in your dog and minimize some of the symptoms associated with allergic reactions. Common situations in which a pet owner may be able to give their dog Benadryl include¹:

• Itchiness, excessive licking, hair loss
• Runny nose and eyes
• Coughing and sneezing
• Swelling and inflammation
• Allergy-induced asthma

Benadryl can also be a common first line of defense against anaphylaxis, a severe allergic reaction that can cause difficulty breathing, vomiting, excessive salivation or drooling, and diarrhea.

If you believe your dog is experiencing an allergic reaction, it’s best to contact your vet to determine whether Benadryl is a good next step and get instructions for dosage and frequency.

In some cases, diphenhydramine for dogs may be used to mitigate the side effects of other conditions like¹:

• Motion sickness
• Mast cell tumors
• Heartworm treatments

Again, these applications should be given according to your vet’s recommendations surrounding dosage, frequency, and more.

Side Effects of Benadryl in Dogs

If your vet recommends Benadryl, it’s important to be aware of the side effects. While most dogs will tolerate Benadryl well, you may see a few of these common side effects¹:

• Drowsiness: This is a common side effect of Benadryl for dogs, especially if your dog is taking the medication for the first time.
• Dry mouth: Make sure your dog has plenty of water to stay comfortable throughout the duration of their Benadryl treatment.
• Urinary retention: If you notice your dog going to the bathroom less often, you may want to give your dog a few extra minutes outside. Reach out to your veterinarian if urinary retention is prolonged.
• Hypersalivation: Diphenhydramine for dogs may cause excessive salivation.
• Increased heart rate: Pay attention to your dog’s body language and behavior. If they exhibit unusual behavior and are seemingly in distress, notify your veterinarian immediately.
• Rapid breathing: If your dog seems unable to get enough oxygen, contact your vet.

In addition to these side effects, your dog may experience less common side effects like diarrhea, vomiting, and a change in appetite.

Again, if you have any concerns about the side effects your dog may experience from Benadryl or their severity, we recommend you contact a vet.

Benadryl Dosage: How Much Can You Give to a Dog?

Properly dosing Benadryl for dogs is a must. While some guidance is available on dosage based on your dog’s weight, you always need to talk to your veterinarian before giving your dog Benadryl. They can confirm proper dosage and help keep your dog healthy and safe.

The average dosage for antihistamines is 2 to 4 mg of Benadryl per kilogram of body weight up to 2 to 3 times daily.¹ Here is an example calculation below:

Say your dog weighs 100 pounds, or 45 kg. 45 kg x 2 mg of Benadryl = 90 mg of Benadryl, and 45 kg x 4 mg of Benadryl = 180 mg of Benadryl. According to general guidance, the recommended range is 90 to 180 mg of Benadryl per dose.

Remember that this is only the recommended dose. Your vet can give guidance on where you should fall in this range. They may suggest starting with a lower dose, only increasing it if you feel your dog's health is not improving. You also need to talk to your veterinarian to see if there are other issues you need to consider. For example, your dog might be taking other medications that can impact the rate at which their body metabolizes Benadryl.

How Often Can I Give My Dog Benadryl?

Another consideration when administering Benadryl to your dog is the frequency. Even though the recommendation is 2 to 4 mg per kg of body weight, giving your dog Benadryl too frequently can also lead to an overdose. Guidance surrounding frequency recommends administering 2 to 3 times per day.¹

Again, consulting a veterinarian is a must. Overdosing on Benadryl is possible, and other medications can influence its effects.

How Long Does Benadryl Last In A Dog?

Generally speaking, a dose of Benadryl lasts in your dog’s system between 8 and 12 hours. That said, several factors play a role in how quickly your dog metabolizes Benadryl, including:

• Breed
• Other medications
• Kidney function
• Liver function

If your dog is experiencing side effects from Benadryl, you should expect these to wane past the 8 to 12-hour timeline and disappear completely within 24 hours of their last dose. If your dog is still experiencing side effects more than 24 hours after their last dose of Benadryl, reach out to your vet to ensure they’re not experiencing complications.

What Happens if a Dog Overdoses on Benadryl?

Benadryl overdose can range from mild to severe, with symptoms becoming more dangerous as severity increases. Look out for these signs that indicate your dog may be experiencing a Benadryl overdose:

• Sedation and lethargy
• Clumsiness
• Dangerously fast or slow heartbeat
• Dilated pupils in well-lit spaces
• Slow or shallow breathing
• Seizures

Even if you’re administering diphenhydramine for dogs per a veterinarian’s instructions, it’s vital to be vigilant for signs of a Benadryl overdose. If you do suspect an overdose, reach out to your vet immediately. In severe cases, Benadryl overdose can be fatal.

Alternatives to Benadryl for Dogs

Benadryl is not the only form of antihistamine for dogs, and in some cases, other antihistamines or medications may be better. Depending on the condition you’re attempting to treat, consider the following alternatives to Benadryl for dogs:

• For allergies: You may be able to manage your dog’s allergic reactions using more precise medications, like medicated shampoos for skin allergies or prescription medications that are designed to target a specific type of allergic reaction.
• For anxiety: While some turn to Benadryl for treating dog anxiety, it's far from the most effective solution. Medications like trazodone, combined with behavioral training specifically designed to address anxiety, yield significantly better results.

Talk to your vet about whether there might be a more effective alternative to Benadryl for your dog.

Is Benadryl Safe for Dogs: When to Speak to a Vet

Again, talking to a vet before administering Benadryl to your dog is always a good idea, especially if using it for the first time. Your vet may want to discuss the following factors before determining whether Benadryl will be a safe and effective treatment for your dog:

• Medical history: Kidney and liver conditions can dramatically impact how your dog metabolizes diphenhydramine. Inform your vet if your dog has any.
• Current medications: Let your vet know if you give your dog any prescription or over-the-counter medications, supplements, herbs, or anything else with medicinal properties. Your vet can help determine whether there are any interactions that require a different dosage or make Benadryl an unsafe option for your dog.
• Medication history: Your vet may also ask you to think about other medications your dog has taken in the past. This can help them determine how your dog will respond to Benadryl.
• Possible underlying conditions: What you think may be an allergic reaction could be a symptom of a different underlying condition.
• Possible allergies: If your dog has a history of allergic reactions, you need to talk about this with your veterinarian. Your veterinarian will want to gauge the possibility of your dog developing an allergic reaction to Benadryl. Even though it is unusual for a dog to be allergic to Benadryl, this is still something you need to be vigilant about.

After you have discussed these issues with your veterinarian, they should let you know if it is safe to give your dog Benadryl. Then, based on your vet's advice, you can move forward accordingly. Remember that you must monitor how your dog responds to Benadryl. If you have any concerns about how your dog responds to Benadryl, reach out to your vet as soon as possible.

FAQS

Is there a difference between human Benadryl and dog Benadryl?

No, there is no difference since Benadryl is a brand of diphenhydramine that's specifically made for humans. However, there are other forms of diphenhydramine available that are explicitly made for dogs.

Is Benadryl or Zyrtec better for dogs?

In some cases, Zyrtec may be a better antihistamine for dogs since it doesn’t cause as much drowsiness. Your vet can help you determine whether Benadryl or Zyrtec is better for your dog’s condition.

What is the best antihistamine to give a dog?

There is no single “best” antihistamine for dogs. Finding the right antihistamine for your dog’s needs depends on several factors, including their current condition, overall health, medication usage, and more. Your vet can help you determine the best treatment for your dog’s needs.

What happens if I give my dog too much Benadryl?

Giving your dog too much Benadryl can lead to an overdose. Common overdose symptoms include a rapid heartbeat, dilated pupils, agitation, lethargy, slow and shallow breathing, clumsiness, and seizures. If your pet has any of these symptoms, contact an emergency vet as soon as possible.

Always talk to a vet before giving your dog Benadryl to ensure the correct dose is administered.

Will Benadryl calm a dog down?

A common side effect of Benadryl is drowsiness, which can help calm your dog down and make them fall asleep. However, Benadryl should only be used to treat allergic reactions in dogs under the guidance of a veterinarian. If you need help calming your dog, treatments made explicitly for dog anxiety may be better.

Final Notes

Although Benadryl is sold over the counter, it is essential to remember that it is still a powerful medication, especially when given to dogs. To safely administer Benadryl to your dog, you must understand when you can give your dog Benadryl, how much Benadryl you can give your dog, and how often your dog can have Benadryl. Knowing the signs of a Benadryl overdose can also help you save your dog in case of an emergency.

If you are interested in giving your dog Benadryl or want to learn more about other allergy treatments, speak to a Dutch vet today. A licensed vet can help you resolve your pet's allergies through a personalized treatment plan that suits their specific needs–all from the comfort of your home. Plus, Dutch members get free shipping from our online pet pharmacy on all orders. Join Dutch today.