A condition of unusual sensitivity of one individual to one or more substances (may be inhaled, swallowed or came in contact with the skin), witch may be harmless or even beneficial to the majority of other individuals.

In sensitive individuals, contact with these substances (allergens) can produce a variety of symptoms in varying degrees ranging from slight itching to swelling of the tissues and organs, mild runny nose to sever asthmatic attacks, general tiredness of fatigue to severe anaphylaxis.

The ingested, inhaled or contacted allergen is capable of alerting the immune system of the body. The frightened and confused immune system then commands the white blood cells to produce immunoglobulins type E (IgE) to stimulate the release of the chemical defense forces, like histamines, from the mast cells.

These chemical radiators are released as part of the body’s immune response to the foreign substances; and these chemicals produces abnormal physical, physiological and psychological symptoms in sensitive person.

Above information is quoted from Dr. Devi  S. Nambudripad 

 “SAY GOODBYE TO ILLNESS (2002) EDELTA PUBLISHING, CO.