Itchy Dogs and Cats–A 3 Part Series: Part 3

Written by Dr. Angie Ahlstrom

Part 3: Environmental Allergies

Similar to humans, dogs and cats can have allergies to substances in their environment. Common environmental allergies include pollen (weed, grass, and tree) and dust mites. There are several promising treatment option for environmental allergies, but first we have to diagnose which allergen is the culprit for your dog or cat.

The first thing that owners generally notice when their pet has environmental allergies (“atopy”) is very irritated and itchy skin. This is due to an overgrowth of the pet’s normal skin bacteria. While this overgrowth can be seen with any allergy, including food and flea allergy, it is very common in atopy animals. Treatment of this skin infection generally includes antibiotics (to control the bacteria), antimicrobial shampoos (to provide more immediate relief of skin bacterial overgrowth), and—in severely itchy patients—steroids to decrease the itchy immune response against the skin.

As in humans, environmental allergies in pets are typically seasonal; they flare up most often during Spring and Fall. Therefore, if your pet is itchy year-round, he or she is more commonly allergic to food or to indoor allergens like dust mites. Make notes of when your dog or cat is most itchy; if a pattern of season allergies begins to evolve, be sure to pass this information on to your veterinarian.

Diagnosis of environmental allergies can be performed two different ways: skin testing and blood testing. Your veterinarian will decide which of these approaches is best for your pet. In certain cases, they may elect to perform both tests.

  • Skin testing: For this test, your cat or dog’s side is shaved and series of dots are drawn on the bare skin. Small amounts of known allergens are injected into the skin at each of these dots. The level of reaction against the allergens is recorded. Based on the amount of reaction your pet has to each allergen, your veterinarian will determine if the allergen is a likely culprit of pet’s itchiness.
  • Blood testing: This test also measures the level of reaction against a variety of potential allergens. Blood is drawn and sent to a laboratory; results are then interpreted by your veterinarian to determine the most potent allergens for your pet.

There are several different options for treatment of environmental allergens. They can be divided into 2 categories—prescription medications and immunotherapy.

Medications: Medications are aimed at decreasing or eliminating the symptoms of atopy.

  • Anti-histamines: these are generally only effective for very mild allergies. There are several different prescription options available.
  • Steroids: these are potent anti-itch medications to decrease the body’s immune response against allergens. Long-term steroid use is not recommended as these medications have multiple side effects including delayed healing time and liver stress.
  • Cyclosporine (brand name Atopica): this is a powerful immunosuppressive which is used for long-term allergy management. It has fewer concerning side-effects when compared to steroids.

Immunotherapy: Immunotherapy options are aimed at curing patients of their allergies. The goal is to eliminate the body’s need to mount an allergic response. This is achieved by slowly desensitizing the body to the allergens.

  • Allergy injections: With this treatment, low concentrations of the allergens are injected under your pet’s skin daily. Over time, the concentration of the allergens is increased until they reach a maximum concentration. The injections become less frequent, generally decreasing to approximately every 30 days. Note that this treatment is life-long. If the injections are stopped, the allergy will generally return and the process must be started over again. Your veterinary staff can help teach you how to give these injections.
  • Sub-lingual (under the tongue) allergy drops: Science has shown that much of the immune response is developed through the introduction of allergens in the mouth. Therefore, immunotherapy can also be delivered this way. The basic concept of these drops is similar to the allergy injections—the concentration of allergens is slowly increased over time until reaching a maximum concentration. Unlike the allergy injections, allergy drops must be continued every other day for life. This is an option for dogs or owners that do not feel comfortable giving at-home injections.

Schedule an appointment with your veterinarian today to discuss your pet’s allergies and the potential treatments.


This concludes our series on itchy dogs and cats. If you are concerned about your pet’s skin, call your veterinarian to schedule an appointment today!

Leave a comment