It is very necessary for our body to be safe and far away from foreign body. Allergen is nothing but it is a small substance which causes threat to our body. Our body by mistake this allergen into our body. And if a series of such thing happen to our body then it said that our body caused by allergic Cascade.
It is our immune system which protects our body from any foreign substance which is harmful to our body. Due to series of this allergen action our body causes some symptoms. You have see some people sneezing all the time the reason behind this is allergen. You also got runny nose diarrhea, coughing, sore throat, and also hive.
The only and only way to get ride from allergen is that to keep far away from any type of foreign substance. For example some people who get allergy from food material so that they can not only eat food but as well as can taste all those substance which consist of food materials.