An allergy is nothing more than an excessive reaction of the body due to contact with an allergen. There are currently various types of allergy, e.g. to drugs, cosmetics, bacteria, viruses, chemicals, foods, fragrances, flowers or even water. For most patients, an allergic reaction manifests itself through coughing, runny nose, sore and red eyes, rashes, itching all over the body and problems with the digestive system.