Why Antihistamines Fail to Control Itch in Dogs

Why Antihistamines Fail to Control Itch in Dogs

An itchy dog is a stress for the whole family. When our dogs are uncomfortable, we naturally feel for them and want to relieve their symptoms as quickly as possible. Antihistamines, like Benadryl®, have historically been an easy over-the-counter option to provide people (and pets) some relief. Yet, studies have demonstrated that while antihistamines may relieve respiratory allergies in humans, they had little or no effect on skin allergies in dogs[1,3].

Can Dog Itch Be Difficult to Treat?

Itchy dogs can be frustrating to treat — for the dog, the owner, and sometimes even the veterinarian. There are a variety of treatments that may be recommended for your itchy dog, including:

  • Allergy medications to control itch and skin inflammation
  • Anti-parasite treatments like oral or topical flea/tick preventatives
  • Antibiotics or antifungals to treat the underlying infection(s)
  • Topical therapy like shampoos, conditioners, and sprays

For uncomplicated itchy dog causes like fleas, treatment is easy to administer and can be up to 100% effective. For more complicated cases like dogs with chronic allergies and secondary infections, it can be more challenging to completely eliminate the symptoms but there are treatment options available that keep things easy for you and your dog.

What About DIY and Over-the-Counter Options?

While it may be tempting to reach for the anti–itch or scratch relief shampoos and sprays at your pet supply store or to pick up an antihistamine at the drugstore, these may only provide temporary relief at best. Topical therapies may provide minor temporary relief in some mildly itchy dogs, but are not effective alone in controlling itch in most allergic dogs. Let your veterinarian know all of the current medications you are giving, as well as other medical conditions that your dog has, so they can make sure the prescribed medication is safe to use in your dog. They will work with you to identify the underlying cause and develop treatment strategies to prevent itch from recurring, or manage it if it does.

What are Antihistamines and Why Don’t They Work for Most Itchy Dogs?

Allergies in dogs are different than allergies in people. Histamines cause upper respiratory allergies in people, whereas cytokines (not histamines) cause itchy skin in dogs.

For dogs with underlying allergies, antihistamines don't control the cytokines (signaling proteins) that cause inflammation and itch[1]. In fact, the International Committee on Allergic Diseases of Animals lists antihistamines under "Interventions likely to be of little or no benefit to treat acute flares of canine atopic dermatitis[1]." Antihistamines can also cause some unwanted side effects, including sedation, trembling, and panting[2]. In addition, antihistamines can put your dog at risk for worsening allergic itch and secondary infections since they are not treating the underlying cause of the itch.

Alternatives to Treating Itchy Dogs with Antihistamines

Once the underlying cause of your dog's itch has been identified — and even while working to identify the cause — discuss with your veterinarian treatments that are proven to control allergic itch. You'll work together to find an anchor treatment (one single treatment that will control itch most of the time) and then supplement with other treatments depending on how your dog responds.

Work with your veterinarian to determine the underlying cause of your dog's itch and discuss the best approach for treatment and prevention. For pet owners of allergic dogs concerned about antihistamines not working or having side effects, ask your veterinarian about other therapies proven to reduce allergic itch. Managing your dog's itch quickly and effectively will save frustration, time, money, and best of all, give your pet the relief they deserve.

Sam Gilbert, VMD

Sam Gilbert, VMD

Raised in Northern Virginia, Dr. Sam Gilbert received both his BSE and VMD degrees from the University of Pennsylvania. Dr. Gilbert completed a one-year small animal internship and additional surgical training before relocating to New Jersey for roles in the medical device and animal health industries. Dr. Gilbert currently serves as the Zoetis Petcare HQ Medical Lead for pet owner directed initiatives in dermatology and cross-portfolio therapeutic areas. Outside of work, he enjoys spending time with his wife, daughter, and cat.

  1. Marsella, R., Sousa, C. A., Gonzales, A. J., & Fadok, V. A. (2012). Current understanding of the pathophysiologic mechanisms of canine atopic dermatitis. Journal of the American Veterinary Medical Association, 241(2), 194-207.
  2. DeBoer DJ, Griffin CE. The ACVD task force on canine atopic dermatitis (XXI): antihistamine pharmacotherapy. Vet Immunol Immunopathol. 2001 Sep 20;81(3-4):323-9.
  3. Olivry, T., Deboer, D. J., Favrot, C., Jackson, H. A., Mueller, R. S., Nuttall, T., & Prélaud, P. (2015). Treatment of canine atopic dermatitis: 2015 updated guidelines from the International Committee on Allergic Diseases of Animals (ICADA). BMC Veterinary Research, 11(1).