24 January, 2021

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Benadryl For Dogs Side Effects & Benadryl Alternatives

Benadryl for Dogs: Usage, Side Effects, and Other Concerns

The compulsion to head to our medicine cabinet to find something that could treat our dogs with can be strong, yet very dangerous. Due to their differences in anatomy, humans and dogs can react differently to the same medicine. This is why veterinarians caution dog owners against making an uninformed decision when treating their dogs.

Benadryl is one medicine that can be used for both humans and dogs. And while it is always a good idea for you to consult your veterinarian first, here are some facts that you should know about using Benadryl for dogs.

What Is Benadryl for Dogs?

Benadryl®(Johnson and Johnson) is the brand name for a substance known as diphenhydramine HCL. This drug can relieve many of the symptoms directly connected to allergies such as itching, sneezing, and rashes. For dogs, Benadryl® is effective in reducing other symptoms of an allergy. These include:

  • Swelling and inflammation
  • Coughing
  • Sneezing
  • Paw licking/chewing
  • Runny eyes and nose
  • Anaphylactic reactions

Benadryl can also work as a sedative, which could help calm them. Some breeds are also mentally affected by an allergy that manifests through aggression and restlessness. It has also been used by veterinarians as a pre-treatment before introducing a vaccine to the animal.

Dosage of Benadryl®

Like many other over-the-counter drugs, the dosage of Benadryl® for dogs is dependent on the size and weight of that particular breed. As such, the standard for Benadryl® application is 1 mg per pound of body weight. It can  be administered orally to up 2 to 3 times a day until the symptoms have stopped manifesting.

If the dog is already experiencing an acute allergic reaction, it is recommended that you skip the oral administration altogether and visit the vet. Some allergic conditions require a combination of medicine in order to be effectively addressed.

Side Effects of Benadryl®

Benadryl®  can cause some effects to manifest on your dog, especially through repeated dosages. As a mild sedative, Benadryl®can make your dog drowsy.. Other common side effects include drying in the mouth,.

There also some rare and uncommon side effects that any dog owner should be aware of if they administer  the drug orally their pets:  changes in appetite, excessive salivation, rapid breathing and increased heart rate, and urinary retention.

Also, Benadryl® is known to cause some adverse reactions if the dog has been diagnosed with any of the following conditions:


  • Bladder neck obstruction
  • Seizures
  • Allergic lung disease
  • Pregnancy
  • Angle closure glaucoma
  • Hypertension

Cost of Benadryl for Dogs

Benadryl® is one of the less expensive over-the-counter drugs that you could purchase for dogs. The price for a capsule bottle that contains 500 to 1000 capsules can go in between $2.00 and $5.00 in drug stores and online suppliers.

Standard Benadryl® tablets come in 25 mg units that is perfect for administering on average-sized dogs like Labradors and Collies. There is also a 50mg tablet that is advisable for larger and heavier dogs. For smaller dogs, it is best to coordinate the dosage with the veterinarian. This way, unpleasant side effects could be avoided.

Interactions with Other Drugs

Benadryl® is known to react negatively if used in tandem with other medications. It reportedly has an addictive effect when combined with other sedatives, and other anticholinergic substances.

When used with medication that contains epinephrine Benadryl®is known to enhance the effects of the substance. As such, Benadryl® is not to be used when treating allergic reactions for insect bites and stings if the dog already has taken an epinephrine-based tablet.

Lastly, Benadryl® is known to lessen the effects of warfarin and heparin. If the dog is on medication for diseases like pancreatitis and laminitis or is recovering from burns, the use of Benadryl® is not advised.

Due to this, it is highly recommended that you consult with a veterinarian before attempting to administer the medicine to your dog. They would know if introducing the drug would cause some interactions with other medications or worsen pre-existing conditions.

Ingredients in Benadryl®

The primary ingredient in Benadryl® is a substance known as diphenhydramine HCI, this is an antihistamine. This means its primary purpose is to block receptors mainly on inflammatory cells (Mast cells) to prevent the release of histamine (a content within the cell).  Think of an antihistamine like “locking” a door to a room filled with thousands of tiny balls.  The “key” to unlock the door is something like Ragweed pollen, or a bee sting.  Now, with an antihistamine already in the system, if the pesky key tries to unlock the door, it just won’t open, at least not easily.

Aside from diphenhydramine, Benadryl® also contains other inactive ingredients, most of which are present to allow the powdery substance to be formed into a solid tablet.

  • Stearic acid
  • Pregelatinized starch
  • Microcrystalline cellulose
  • Hypermellose
  • Crospovidone
  • Colloidal silicone dioxide
  • Titanium oxide
  • Talc
  • Candellila wax

Alternatives to Benadryl for Dogs

Although Benadryl® is highly recommended by veterinarians in treating canine allergic reactions, it is not the only option available out there. Here are some natural options that could serve as an alternative to Benadryl®.

  • Collostrum – Usually found in the milk of mothers, Colostrum is known to contain an ingredient called Praline-Rich Polypeptide. This substance targets the immune system and rewires its usual response to allergens.

It can also inhibit the cells that amplify allergic reactions and can create helper and suppressor T-Cells that will suppress the effects of allergic reactions.

  • Mushrooms, Seaweed, and Yeast

These readily available ingredients contain a substance known as beta-glucan. The substance essentially changes the body’s response to allergies by energizing a kind of cell called a macrophage.

This cell, in turn, traps and destroys foreign substances coursing through the body such as viruses and allergens. It also has an added benefit of keeping the dog active, unlike Benadryl®, which sedates them.



DR Gullamune Hoareau

Reviewed By Dr. Gullamune Hoareau

Dr. Hoareau earned his veterinary degree from the Toulouse National Veterinary School, France. He completed a residency from the University of California-Davis and is now board-certified by both the American and European Colleges of Veterinary Emergency and Critical Care. Dr. Hoareau holds a PhD from the University of California-Davis in Integrative Pathobiology, specifically in resuscitation and haemorrhage control. He completed a research fellowship in military trauma and critical illness. His interests include haemorrhage control, cardiac arrest, and working dog health.


University of utah