Publisher's Synopsis
An immune system reaction to a substance that is not normally harmful to the body is what we call an allergy. We refer to these noxious invaders as allergens. Certain foods, pollen, and animal dander are common examples.
The immune system protects you from disease-causing microbes. This is done by attacking anything it determines poses a threat to your physical safety. Inflammation, sneezing, and other symptoms can occur in response to allergens.