What is an "allergen"?

What is an "allergen"?

Harold Kaiser (Practicing Allergist and Clinical Professor of Medicine, University of Minnesota Medical School) gives expert video advice on: What causes allergies?; What happens in my body when I have an allergic reaction?; Are allergies becoming more common? and more...

An allergen is a substance that evokes an allergic response. In other words, if I'm not allergic to peanuts and I eat some peanuts, I eat some peanuts. If you are allergic to peanuts and you eat some peanuts, then your body reacts with a big reaction: inflammation, rash, shortness of breath, different things like that. An allergen is essentially an atypical, unusual response to something that people normally have no problems with. There is a thought that the word "allergy" derives from a Greek word "allos" meaning atypical or unusual. You're getting an atypical, unusual reaction to something that doesn't bother everybody.