Allergies can often be debilitating to those affected. If you have an allergy, your body is reacting to something you inhaled, touched or ate. The substances that trigger an allergic reaction are called allergens. A very small amount of certain allergens is put into your skin by making a small indentation or “prick” on the surface of your skin. If you have allergies, just a little swelling will occur where the allergen(s) which you are allergic to was introduced.