To be sure that a person is allergic to something, a medical doctor can perform some simple tests. The most popular ones are called the skin-prick test and the IgE test.
In the skin-prick test, the doctor or nurse puts tiny amounts of different allergens just under your skin. If you are allergic, you will develop a red bump where the allergen was placed. The doctor can tell how allergic you are by the size of the red bump. In the IgE test, the doctor will do some blood tests to see whether you have a high amount of IgE in your bloodstream, or IgE specific to some common allergens.
If you have a positive allergy test, and you know which allergen(s) you are allergic to, the best treatment is to avoid contact with those allergens. However, it is easier to avoid contact with some allergens, like peanuts or milk, than it is to avoid airborne allergens, like dust or pollen. Can you imagine not being exposed to any pollen during spring? Since it is very hard to avoid some allergens completely, particularly the airborne ones, medicines have been developed to reduce inflammation and stop the allergic reaction from occurring.

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