An allergy is the result of an overreaction by the body's immune system in the presence of an allergen. However, how does that work, exactly? Knowing how the immune system responds to allergies will help you to  understand what is happening when you suffer that runny nose, itchy rash or stomach upset.

There is little good news associated with finding out that you are allergic. Unfortunately, all too many folks have first hand experience of allergies and allergic reactions. The itchy eyes, runny nose, skin rash and other assorted symptoms are uncomfortably recognizable. However a more exact medical definition of the causes of allergies may well be helpful, since it is the first step towards diagnosis along with treatment for the correct condition.