Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to some substances, causing different reactions as red eyes, an itchy rash, runny nose, shortness of breath, or swelling. This hypersensitivity also means that our organism reacts negatively on something in the environment that usually causes little or no problem in most people.
The allergic reaction may be caused by different types of contacts with the allergen: that may be the contact via airway or even the direct contact of the allergen with the skin.
The allergy is quite "young" illness which is known in our world only from the beginning of the 20th century. The term "allergy" was used for the first time by an Austrian scientist Clemens von Pirquet in 1906. That's why nowadays allergic reactions are still not fully examined by the specialists and we don't have enough information about its' origins and the ways of treatment. All the modern medicine have the only effect – they just block the symptoms, moreover, the regular use may cause digestive system problems, that's why even nowadays the most effective way to combat allergies is to see off the main problem – the allergen itself.