What are allergens?

Q:  What are allergens, and what are the most common allergens that aggravate eczema?

A:  Allergens are any molecule in the environment that can penetrate skin and cause an inflammatory response. Most allergens cause a rash in only a small number of people, but some like poison ivy cause a rash in most people who have skin contact with it. Allergic contact dermatitis usually develops to small, non-protein molecules such as preservatives or metals. Atopic dermatitis patients can also develop contact dermatitis to plant proteins such as oat or dandelion.