Can dogs use Benadryl?

  • Benadryl can be used safely on dogs; however, the U.S. Food and Drug Administration has not approved Benadryl for veterinary use(1).
  • Studies reveal several potential side effects of Benadryl on dogs, including sedation, dry mouth, urinary retention, hypersalivation, increased heart rate, and rapid breathing(2). Overdose or incorrectly administered Benadryl can be fatal to dogs, especially those with pre-existing medical conditions(3).
  • Natural alternatives like quercetin(4), aloe vera(5), and CBD oil(6) could alleviate the common symptoms treated by Benadryl.
  • Among these natural remedies, CBD oil can relieve most symptoms like allergies(7), travel anxieties(8), motion sickness(9), and mast cell tumors(10).
  • Before using CBD on their dogs, dog owners must consult with their veterinarian to manage risks and safety issues.

What is Benadryl?

Benadryl is a brand name and over-the-counter medication with the active ingredient diphenhydramine HCL.

Diphenhydramine is a first-generation antihistamine and ethanolamine(11). It treats allergy symptoms such as itchiness, sneezing, runny nose, and watery eyes. It also alleviates motion sickness, hives, insect bites, and symptoms of the common cold.

Because of its sedative properties, Diphenhydramine is also used as a mild sleeping aid(12)

Can Benadryl be Used on Dogs?

According to the American Kennel Club (AKC)(13), while the Food and Drug Administration (FDA) has not approved Benadryl for veterinary use, it is safe for use in dogs and cats.

AKC says that Benadryl can help treat mild to moderate dog allergies, be it food allergies, environmental allergies, or seasonal allergies. It is also prescribed for dogs with mast cell tumors and those undergoing heartworm treatment(14).

Benadryl can also relieve a dog’s travel anxiety and motion sickness during car rides(15).

Benadryl Dosage for Dogs

According to Pet MD’s Dr. Jessica Vogelsang, DVM, (16), the standard dosage for Benadryl tablets for dogs is 1mg per pound of body weight and could be given two to three times a day.

When administering liquid Benadryl to dogs, using children’s liquid formula is safer as most do not contain alcohol(17). For small dogs, it is also better to use Benadryl tablets for kids. 

For the correct dosage, dog owners are still encouraged to consult with their veterinarian as an overdose or incorrect administration of Benadryl can be fatal, especially to dogs with pre-existing medical conditions(18).

Signs of Benadryl overdose(19):

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

Dogs that have overdosed on Benadryl or have shown adverse reactions like symptoms of allergies must be brought to a veterinary hospital immediately.

Side Effects of Benadryl on Dogs

Common side effects of Benadryl(20):

  • Sedation
  • Dry mouth
  • Urinary retention
  • Hypersalivation
  • Increased heart rate
  • Rapid breathing

Rare side effects of Benadryl:

  • Diarrhea
  • Vomiting
  • Decreased appetite

When it comes to using Benadryl, there are several do’s and don’ts that pet owners should observe to preserve a dog’s health.

Do not administer Benadryl to a pet if it has the following conditions(21):

  • Angle-closure glaucoma
  • Severe heart failure
  • Prostatic hypertrophy
  • Bladder neck obstruction
  • Seizure disorders
  • High blood pressure
  • Allergic lung disease
  • Pregnancy

Natural Alternatives to Benadryl for Dogs

Even if Benadryl and other over-the-counter drugs are readily available in most medicine cabinets, Dr. Lynn Buzhardt, DVM advises that it is still best to consult with a veterinarian.

 According to Buzhardt, though usually safe, antihistamines make some dogs drowsy and hyperactive. Some ingredients, like decongestants, are also unsafe for pets. 

It’s unwise to be lulled into a false sense of security by assuming that drugs are safe just because they can be purchased without a prescription,” says Buzhardt in a 2016 article on over-the-counter medications for dogs(22).

It is no surprise that pet parents are turning to natural remedies instead of using over-the-counter drugs on their pets.

Quercetin and Dogs

Referred to by veterinarians as nature’s Benadryl, quercetin is a flavonoid found in fruit and vegetable peelings that can help dogs that are suffering from environmental allergies(23). It also has high antioxidant, anti-inflammatory, and anti-allergic properties that help alleviate allergies in both humans and animals alike(24).

Quercetin comes in pill and capsule form.

Aloe Vera and Dogs

In a 2017 article on natural remedies for dogs with itchy skin, Dr. Diane Richter prescribes aloe vera as a natural remedy to promote healing in dogs and to soothe their skin(25).

Richter adds that if the aloe vera is in lotion form, it should be alcohol-free because alcohol can burn the skin.

 Aside from store-bought products, aloe vera fresh gel could be sourced from aloe vera plants at home.

Magnesium lactate and alprogen are aloe vera’s chemical components that give it its anti-allergic effects(26).

CBD Oil and Dogs

The endocannabinoid system (ECS) is the system that regulates the functions of cannabinoids. A 2019 study on the ECS of animals reveals that the ECS is universal to all animal species except insects and that it “possesses essentially the same benefits regardless of the species under review. (27)

Hence, if CBD (cannabidiol), a non-psychoactive cannabinoid, can be given to humans for medical purposes, it is suggested that it can be administered to dogs as well.

According to Dr. Jerry Klein, the Chief Veterinary Officer of the American Kennel Club (AKC), CBD oil is used to treat dogs because of its many benefits, including its anti-inflammatory properties, anti-nausea effects, appetite stimulation, cardiac benefits, anti-anxiety impact, and possible but inconclusive anti-cancer benefits(28).

Several studies have also shown that CBD can help alleviate the symptoms that Benadryl is used for, such as allergies, travel anxiety, motion sickness, and mast cell tumors. 

A study in 2007 revealed that CBD could help reduce allergic responses in the skin (29) because of the protective role of the ECS.

CBD is also useful when traveling with anxious pets. Like Benadryl, it has sedative effects, thereby aiding in the relaxation of pets; this is supported by a 2016 scientific report that says CBD helps relieve anxiety and pain in animals and helps with their sleep(30).

CBD can also be used to treat motion sickness as it reduces vomiting and nausea-like behavior (31).

A 2016 research study shows that cannabinoids are effective in increasing tumor growth and invasion(32). Hence, it can help in the treatment of mast cell tumors in dogs.

Potential side effects of CBD on dogs include dry mouth, lowered blood pressure, and drowsiness(33).

Because the U.S. Food and Drug Administration (FDA) has not approved CBD, there is no dosing chart for dogs.

Despite this, CBD use is safe. It is advised that dog owners give their pets small amounts and then monitor CBD’s effects.

CBD may be administered to dogs through CBD pet tinctures that may be mixed with pet food, given orally, or used in massages.

CBD can also be applied to a dog’s skin as it also comes in topical forms like 

CBD hemp oil, creams, salve, or balms.

For pet parents who have plans of including CBD in their pet’s regimen, it is best to inform their veterinarian before doing so.

CBD and Benadryl

There are no known interactions between CBD and Benadryl, but there is a potential risk when these are taken together(34).

The cytochrome P450 enzyme system metabolizes both CBD and Benadryl. CBD could act as a competitive inhibitor of cytochrome P450, thereby halting the enzymes’ action on substances they normally metabolize like Benadryl.

Conclusion

While the use of Benadryl on dogs is safe, it has several side effects that can be concerning to a pet parent. Benadryl cannot just be administered, especially to dogs that already have pre-existing conditions. 

The dosage of Benadryl should be 1mg per pound of body weight and could be given to dogs two to three times a day. 

Benadryl can treat symptoms like allergies, travel anxieties, motion sickness, and mast cell tumors in dogs, but natural alternatives like CBD can also help treat these. 

Despite these benefits from CBD, it also has side effects like dry mouth, drowsiness, and lowered blood pressure.

Dog owners should consult with their veterinarian before administering CBD to their pets.

No scientific studies are recommending the use of CBD alongside Benadryl as CBD could affect the metabolizing of Benadryl.


  1. Burke, Anna. “Benadryl for Dogs: Dosage, Side Effects, & Uses.” American Kennel Club, American Kennel Club, 7 Mar. 2018, www.akc.org/expert-advice/health/benadryl-for-dogs/.
  2. Burke, Anna. “Benadryl for Dogs: Dosage, Side Effects, & Uses.” American Kennel Club, American Kennel Club, 7 Mar. 2018, www.akc.org/expert-advice/health/benadryl-for-dogs/.
  3. Buchweitz, John P, et al. “Fatal Diphenhydramine Poisoning in a Dog.” The Canadian Veterinary Journal = La Revue Veterinaire Canadienne, Canadian Veterinary Medical Association, Nov. 2014, www.ncbi.nlm.nih.gov/pmc/articles/PMC4204843/.
  4. PetMD Editorial. “Natural Supplements for Dogs With Itchy Skin.” PetMD, www.petmd.com/dog/natural-supplements-dogs-itchy-skin?page=2.
  5. Sullivan, Megan. “5 Natural Remedies to Help Your Itchy Dog.” PetMD, 10 Mar. 2017, www.petmd.com/dog/slideshows/5-natural-remedies-help-itchy-dog?view_all=1.
  6. Karsak, Meliha, et al. “Attenuation of Allergic Contact Dermatitis Through the Endocannabinoid System.” Science, American Association for the Advancement of Science, 8 June 2007, science.sciencemag.org/content/316/5830/1494.long.
  7. Ibid.
  8. Kogan LR, Hellyer PW, Robinson NG. Consumers’ perceptions of hemp products for animals. J Am Holist Vet Med Assoc. (2016) 42:40–8. [Google Scholar] — http://www.le-comptoir-malin.com/medias/files/cbd-animaux-ahvma-2016-v42-hemp-article.pdf
  9. Rock, E M, et al. “Cannabidiol, a Non-Psychotropic Component of Cannabis, Attenuates Vomiting and Nausea-like Behaviour via Indirect Agonism of 5-HT(1A) Somatodendritic Autoreceptors in the Dorsal Raphe Nucleus.” British Journal of Pharmacology, Blackwell Publishing Ltd, Apr. 2012, www.ncbi.nlm.nih.gov/pubmed/21827451.
  10. Ladin, Daniel A et al. “Preclinical and Clinical Assessment of Cannabinoids as Anti-Cancer Agents.” Frontiers in pharmacology vol. 7 361. 7 Oct. 2016, doi:10.3389/fphar.2016.00361
  11. National Center for Biotechnology Information. PubChem Database. Diphenhydramine, CID=3100, https://pubchem.ncbi.nlm.nih.gov/compound/Diphenhydramine (accessed on Apr. 29, 2020)
  12. Ibid.
  13. Burke A. (2018 Mar 7). op. cit.
  14. Ibid.
  15. PetMD. “Can I Give My Dog Benadryl and If So, How Much?” PetMD, 27 Jan. 2020, www.petmd.com/dog/care/can-i-give-my-dog-benadryl-and-if-so-how-much.
  16. Ibid.
  17. Burke A. (2018 Mar 7). op. cit.
  18. Buchweitz J. (2014 Nov). op. cit. 
  19. Burke A. (2018 Mar 7). op. cit.
  20. Ibid.
  21. Ibid.
  22. Buchweitz J. (2014 Nov). op. cit. 
  23. PetMD Editorial. op. cit. 
  24. Mlcek, Jiri, et al. “Quercetin and Its Anti-Allergic Immune Response.” Molecules (Basel, Switzerland), MDPI, 12 May 2016, www.ncbi.nlm.nih.gov/pmc/articles/PMC6273625/.
  25. Sullivan M. (2017 Mar 10). op. cit.
  26. Ahlawat, Kulveer Singh, and Bhupender Singh Khatkar. “Processing, Food Applications and Safety of Aloe Vera Products: a Review.” Journal of Food Science and Technology, Springer-Verlag, Oct. 2011, www.ncbi.nlm.nih.gov/pmc/articles/PMC3551117/.
  27. Silver, Robert J. “The Endocannabinoid System of Animals.” Animals: an Open Access Journal from MDPI, MDPI, 16 Sept. 2019, www.ncbi.nlm.nih.gov/pmc/articles/PMC6770351/.
  28. Kriss, Randa. “CBD Oil For Dogs: What You Need To Know.” American Kennel Club, American Kennel Club, 28 Oct. 2019, www.akc.org/expert-advice/health/cbd-oil-dogs/.
  29. Karsak M. (2007 June 8). op. cit. 
  30. Kogan LR. (2016) op. cit.
  31. Rock EM. (2012 April). op. cit.  
  32. Ladin D. (2016 Oct 7). op. cit. 
  33. Kriss R. (2019, Oct 27). op. cit.
  34. Pharmotech SA. CBD Drug Interactions. Retrieved from https://pharmotech.ch/cbd-drug-interactions/
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