Swollen eyes, tongue and throat, runny nose, itching, headache, tachycardia, diarrhea, shortness of breath and many other common ailments may actually be allergy symptoms. Hypersensitivity to an allergen (the triggering cause of allergy) manifests itself in a more or less obvious way, but most of the time it is neglected or delegated to other factors. The allergy test is carried out in the laboratory and is used to identify the substances that cause these diseases.  One or more allergies not identified can lead to serious diseases.