Can You Give a Dog Benadryl?

When our beloved canine companion is suffering, it’s tempting to reach into our medicine cabinets to offer relief. But humans and dogs react very differently to medications, and what might help you feel better may harm your dog. However, there are some medications that are safe for dogs when used appropriately.


Benadryl is a brand name for diphenhydramine, an antihistamine used to treat allergy or hay fever symptoms. It is one of the few over-the-counter medications veterinarians will have owners administer to their dog at home. 


Make sure to consult with your vet before giving your dog any human medication. If you do get the green light for Benadryl, here’s all you need to know.

What does Benadryl do?

Benadryl blocks the actions of histamine, which is a naturally occurring chemical produced in the body as a response to allergies, infections, or injury. It is often used to treat allergic reactions to insect bites or stings, and pre-treat possible reactions to vaccines.

Can I give Benadryl to my dog?

Benadryl is not yet FDA-approved for veterinary use, but it is commonly used in veterinary practices and considered safe for dogs and cats. Vets will recommend administering to dogs to treat allergies, travel anxiety, and motion sickness.

Is Benadryl safe for dogs?

When used according to the instructions of a veterinarian, Benadryl is a relatively safe and effective medication. Observe your dog closely the first time you administer Benadryl, as you would with any new medication. 

When should I use Benadryl for my dog?

Benadryl is recommended for dogs with mild-to-moderate allergies, including seasonal allergies, environmental allergies, food allergies, and allergic reactions to insect or snake bites. It is also commonly used to treat skin allergies.


If your dog has the following allergy symptoms, Benadryl may help:

  • Itching
  • Redness
  • Swelling/Inflammation
  • Hives
  • Coughing
  • Sneezing
  • Anaphylactic reaction

NOTE: It is possible to develop an allergic reaction to Benadryl itself. If your dog is having an acute allergic reaction (facial swelling, difficulty breathing, excessive salivation or drooling, vomiting, or diarrhea), go straight to the vet. 

When should I not use Benadryl?

Just like with humans, giving medications to dogs can potentially interact with other medications or worsen pre-existing conditions. Possible conditions that would restrict Benadryl use for your dog include:


  • Glaucoma
  • High blood pressure
  • Cardiovascular disease
  • Bladder neck obstruction
  • Pregnancy
  • Allergic lung disease

Also, do not give other sinus or cold medicines containing diphenhydramine to your dog while he/she is on Benadryl.

How much Benadryl can I give my dog?

Typically, a dose of 2-4 mg of Benadryl per kilogram (1 mg per pound) of body weight is administered two to three times a day. Most OTC Benadryl tablets are 25 mg, so would be appropriate for a 25-pound dog. 


However, this dosage can vary, depending on any medical conditions your dog may have. It’s best to consult your vet for the correct Benadryl dosage for dogs. Benadryl is not recommended for pregnant or nursing dogs.


Benadryl typically takes around 30 minutes to start working. If you plan on using it to treat motion sickness or travel anxiety, plan accordingly.

How do I give Benadryl to my dog?

While you should consult your veterinarian for the appropriate dosage for the type of Benadryl you plan to use, here are some general guidelines:


  • Never use time-release capsules, because they absorb differently in dogs and might also break open when chewed.
  • If you want to use a liquid Benadryl, choose a children’s formula.
  • Children’s Benadryl pills or tablets can be used for very small dogs.
  • Liquid Benadryl dosage is different than the dosage for pills.

Can I use generic brands?

Benadryl is one name brand of the drug diphenhydramine. You can use generic brands of the same medication for your dog. 

Are there side effects?

One of the common side effects of Benadryl is drowsiness. This can help calm anxious dogs, and can be used to relieve symptoms of mild-to-moderate travel anxiety. It may also help relieve motion sickness.


Other side effects include:

  • Dry mouth
  • Rapid breathing
  • Increased heart rate
  • Hypersalivation
  • Increased or decreased appetite (rare)
  • Diarrhea (rare)
  • Vomiting (rare)

Most side effects occur within the first hour, so make sure to monitor your dog carefully. If you have any concerns with side effects, contact your veterinarian.

Is it possible for my dog to overdose?

Yes, a dog can suffer an overdose on Benadryl. Watch for these warning signs:


  • Dilated pupils
  • Agitation
  • Constipation
  • Rapid heartbeat
  • Seizures

Contact your vet or emergency veterinary hospital immediately if you worry your dog has overdosed on Benadryl.


How else can I make my dog more comfortable if he has allergies?

One of the more noticeable signs your dog has allergies is itchy skin. No owner likes to see their beloved pet constantly scratching and uncomfortable. To help quickly alleviate itchiness associated with allergies or other conditions, also consider premium dog care products from Equiderma


When used correctly and under the guidance of your vet, Benadryl may give your dog allergy relief so she can enjoy life more fully.

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