What is an "allergen"?

What is an "allergen"?

William Berger (Allergist and Immunologist) gives expert video advice on: What is "asthma"?; Can people die from asthma?; What causes asthma? and more...

We commonly talk about allergies caused by an allergen. An allergen is another word for an antigen that causes an allergic reaction. It is usually a protein, and it can be something that is very commonly found in the environment – a pollen that's in the air, dander that's found on the surface of an animal, or even a dust mite, which is a microscopic insect inside the dust that's in our bedding. Any of these allergens can cause an allergic (or what we refer to as an immunologic) reaction where an allergen hooks on with an antibody that's located on the surface of the cells that line our airways, then cause that cell to burst and release chemicals. Those chemicals are the chemicals that cause the allergic reaction.