Allergy Basics

An allergen is one substance that the body perceives as a risk, triggering a specific chain of events called an allergic cascade. The resistant system protects the body and at times incorrectly identifies a harmless allergen as a threat. The ensuing allergic effect causes symptoms, such as sneezing, coughing, runny nose, irritated throat, diarrhea, nausea, itching and pimples.