What is an allergen?

A foreign protein : An allergen is a foreign protein that the immune system over-reacts to and produces allergic antibody, also called ige, against.

Many things: Anything that causes an allergic reaction, usually an ige mediated reaction. Spring pollen allergens are tree pollens and molds. Summer is mostly grass and mold. Fall is ragweed, other weeds, and mold. Year round allergens in the house are dust mites, pet danders, and , wait for it, mold. Common food allergens are peanut, shellfish, nuts, wheat, and others.