As a result of the immune system being compromised, allergic reactions occur.  Here’s a simplified overview of what happens inside a dog’s body during an allergic reaction.

What is an allergy?

An allergy occurs when the immune system misidentifies a typically harmless substance as one that’s a threat to the body and then produces an unnecessary response to that substance. Things that trigger allergic reactions — such as certain foods, dust, plant pollens, or medicines — are called allergens.

Priming the immune system

White blood cells, which are part of a dog’s (and our) immune systems, make large numbers of small, Y-shaped proteins called antibodies to help protect the body from disease-causing invaders, such as viruses, bacteria, and even some parasites.

Veterinarians take advantage of the sensitization process when they vaccinate your dog against diseases such as parvovirus or rabies. By priming your dog’s immune system to recognize a potential health threat, their body can use those antibodies to fight potential disease-causing viruses and bacteria if exposure occurs.

Unfortunately, and for reasons we still don’t understand, the system sometimes goes a little haywire. White blood cells mistakenly make specific antibodies called immunoglobulin E (IgE) to an allergen such as plant pollen or dust, which is the first step in allergy development.

IgE antibodies bind to the surface of other white blood cells called mast cells and basophils. Because of where they’re located in tissues, mast cells play a critical role in helping to defend the body from potential disease-causing threats. These cells can contribute to allergic reactions like mast cells and to the body’s immune response to internal parasites.

Remembering prior exposure

Once a dog’s immune system has been sensitized to a particular allergen, their body “remembers” that allergen as a threat when the dog encounters it again. Mast cells with that allergen’s specific antibodies bind to the allergen, triggering the mast cells to release the contents of their granules into whatever tissue they happen to be in. Granule contents, whose normal role is to fight infection, cause the symptoms of an allergic reaction.

Histamine and other substances released by mast cells and basophils have different effects in various tissues. In the skin, histamine can produce itching, redness, hives, and swelling in the deep skin layers.

What you can do if you suspect your dog has an allergy

Talk with your veterinarian if your dog is constantly scratching, licking, chewing, and biting at their skin. Furthermore, it is important to have them evaluated to determine the underlying trigger. Nutrition can also help manage some allergies, so be sure to check out this post: The Right Food Can Help a Dog With Sensitive Skin