Allergies (en)

From FitnessWiki

An allergy is a specific immune system response to certain normally harmless substances from our environment, which is then referred to as allergens. The immune system reacts to these substances as a pathogen. In contrast to the normal reaction to some components of an infectious agent in the reaction to an allergen is clearly exaggerated and shooting. In principle, any substance from the environment to cause allergic reactions. This can be plants (eg grass), animal products (eg bee venom), as well as metals (eg nickel) or chemicals (eg preservatives). An allergy is normally only after repeated contact with an allergen (called sensitization). During the first contact yet there are no complaints.