What is an allergic reaction?

What is an allergic reaction?

When you are allergic to something, your immune system overreacts by releasing chemicals like histamine. These chemicals cause symptoms such as itchy, watery eyes and a runny nose. Usually, the symptoms happen in one location of the body.

But in some people, the reaction is more severe, resulting in anaphylaxis. Symptoms include swelling, wheezing, shortness of breath and difficulty swallowing. An anaphylactic reaction affects several areas of the body at once.