Allergy is an abnormal or hyperactive response of the immune system. Allergies occur when immune system reacts to a foreign substance such as pollen, bee venom or pet dander. The substances that cause allergy are called as allergen.
Immune system produces antibodies ,they protect our body against infection. When a person has allergy ,immune system recognizes it and produces antibodies against allergen.when an antibody ome into contact with allergen , the immune system’s reaction can inflame skin,sinuses,airways,or digestive system.
The severity of allergy varies from person to person and it may range from minor irritation to anaphylaxis-potentially life threatening emergency.