Allergy is a type of illness we face when some products or substances are consumed. Those products or substances trigger allergic reaction to the skin and blood of the person. We need to avoid such products or situations which cause allergy in our body. For this we have at least the knowledge of such substances by testing ourselves. Those substances are called allergen. To know which substances causes allergy in our body allergists or immunologists generally tests our blood or skin using little amounts of trouble some allergens. Generally adults and children of any age can go through allergy tests. The symptoms may appear in respiratory systems, in skins or in some other systems. Itching in eyes, nose or throat, nasal congestion, watery eyes or chest congestion are come under respiratory allergy symptoms. Hives, atopic dermatitis and generalized itchiness are part of skin allergies. Anaphylaxis, cramping and diarrhea are some other type of allergies found in our body.