An allergy occurs, when a person becomes sensitized to a particular substance, that provokes an allergic reaction. These substances are known as allergens, or triggers, because they trigger an overreaction by the body’s immune system. There are naturally occurring allergens, such as pollens, environmental substances, such as chemicals, and the foods that we eat, usually proteins, amongst many others.
There are four distinct ways in which allergens can enter the body:
Eating - as with certain foods.
Inhalation - as with dust mites and pollen.
Absorption - through the skin, as with some chemicals and plants.
Injection - some people are allergic to drugs, such as penicillin.
