Skin Allergies: the Prime Suspects

Your Dog’s Scratching Could be a Symptom of an Allergy

Dust, mold and pollen are the most likely instigators of your dog’s allergies. An itch caused by a flea is also an allergic reaction.

Food sensitivity afflicts only a small percentage of dogs. There are two other causes of skin allergies in dogs: fleas and environmental sources such as mold spores and airborne pollen.

Fleas are usually easy to see and diagnose. The itch is often concentrated above the tail, but it can be anywhere on the body. The allergic reaction is actually to flea saliva injected into the dog as the flea feeds.

Fleas and flea allergies are weather-dependent. If you have an itchy dog and it's February in Colorado, chances are he doesn't have fleas. If it's an itchy dog in Florida, fleas are a definite possibility. Flea allergies are treated very easily by using a topical insecticide that kills the fleas before they bite.

Atopic allergies account for the biggest share of allergies in dogs. These are reactions to allergens such as house dust and dust mites, pollens, fungi, and molds.

There is some debate on how the allergens cause the itch. The traditional theory is that they are inhaled, pass through the lungs into the bloodstream, and eventually find their way to the skin. The other thought is that they settle on the skin and migrate between the skin cells to the lower skin layers (the dermis). Either way, there is a reaction of that allergen with an antibody that triggers the release of histamine, causing the itch.

Atopic allergies can be diagnosed with intradermal skin testing, where allergens are injected into the skin to look for reactions. They are treated with medication (antihistamines, cyclosporine, prednisone) and also with allergy injections (hyposensitization). Some breeds of dogs are predisposed to allergies, suggesting there is an inherited tendency for this skin condition.

A version of this article originally appeared in AKC Family Dog.