An allergy is nothing but the abnormal reaction of our immune system when a harmless substance or allergen comes into its contact either by inhaling, swallowing or touching. At least one out of three humans has some kind of allergy. Medical science is yet to figure out why a particular person is allergic to something and somebody else is not. An allergic reaction occurs when the immune system assumes the harmless substance to be dangerous and starts working with extra enthusiasm to defend the body by releasing antibodies which attach themselves to cells commonly found in the airway who in turn release histamines which causes the allergic reaction. Histamines are nothing but chemicals released by the immune system cells to fight against bacteria.

Most common symptoms of allergies are itching, rashes, swelling, runny nose, sneezing and hives.

The most difficult part of allergies is its diagnosis because most of the symptoms are common with other kind of diseases or disorders. For example a runny nose can be due to the common cold instead of an allergy.

Some common allergies are:

* Hay fever is a common allergy in the United States. It is also known as pollen allergy. It usually occurs during the spring and summer season. Its main symptoms are runny nose and sneezing

* Animal allergies are more common with people keeping pets. The allergic reaction here is due to the protein found in animal saliva. Animals keep licking themselves and saliva sticks to their fur which humans constantly come into contact with. Cockroaches are also a common cause of this type of allergy
* Some people do not react well with milk and peanut butter. Food allergies can cause rashes, itchiness etc.
* Some have allergies to drugs like penicillin
* Mold allergies
* Dust mite allergies
* Air borne allergies.

The number of treatments available is as varied as the allergies ranging from home remedies, natural or herbal products, and homeopathy to allopath. However the best way to start treatment is started by doing a few tests to determine what type of allergy a person has and accordingly one can try their best to avoid those particular allergens although with thousands of allergens it is a bit difficult.