An allergic reaction is the immune system's response to the influence of certain external factors called allergens. As allergens can be a variety of substances: pollen, food, dust, medication, pet dander, etc.
Upon contact with allergens having reactions allergic nature that can develop in the nose, on the skin, respiratory tract, digestive system. From the place of supply of allergens on Allergy symptoms: sneezing, nasal congestion, itching, redness, and peeling of the skin etc.
Occur allergic reaction are mild and severe. In severe forms of Allergy the disruption to the functioning of the heart, changes in blood pressure, breathing problems and as a result – death.
Most types of allergic reactions is not curable, but medicine has developed many methods to relieve the symptoms of allergies, among which preventive measures aimed at addressing directly the allergen causing adverse reactions, as well as taking certain (antihistamine) drugs aimed at reducing the activity of allergic reactions.