<P> Common allergens include pollen and certain food . Metals and other substances may also cause problems . Food , insect stings , and medications are common causes of severe reactions . Their development is due to both genetic and environmental factors . The underlying mechanism involves immunoglobulin E antibodies ( IgE ) , part of the body 's immune system , binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine . Diagnosis is typically based on a person 's medical history . Further testing of the skin or blood may be useful in certain cases . Positive tests , however , may not mean there is a significant allergy to the substance in question . </P>
<P> Common allergens include pollen and certain food . Metals and other substances may also cause problems . Food , insect stings , and medications are common causes of severe reactions . Their development is due to both genetic and environmental factors . The underlying mechanism involves immunoglobulin E antibodies ( IgE ) , part of the body 's immune system , binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine . Diagnosis is typically based on a person 's medical history . Further testing of the skin or blood may be useful in certain cases . Positive tests , however , may not mean there is a significant allergy to the substance in question . </P>
a substance that causes an allergic reaction triggers the release of a class of substances known as
a substance that causes an allergic reaction triggers the release of a class of substances known as
histamine
histamine