Allergic reactions occur as a response to an allergen in the body. When a foreign substance enters the body, the immune system is activated and this helps in protecting the body from these foreign substances. The foreign substance is called an antigen and the immune system releases antibodies which combine with these antigens and thus protect the body. There are certain harmless substances called allergens which cause an exaggerated response in the body. Such a response is known as an allergic reaction.
The allergen could be dust, pollen, certain foods, insect bites, animal dander etc. the reactions can occur in one place as a localised skin rash or as a rashes all over the body. The allergic reaction may include one or many symptoms. Most common allergic reactions are minor in nature and are not fatal. Allergic reactions in a way depend totally on the person’s immune system. Allergic reactions can be life threatening in some rare cases.