Allergic Reaction

A hypersensitive immune response to a substance

An allergic reaction can occur when the immune system attacks a normally harmless substance.

This chemical release is irritating and causes itching and swelling mast cells release a variety of strong chemicals, including histamine, into the tissues and blood.

This is how hay fever and allergic pink eye (conjunctivitis) occur. lung airway narrowing and throat tightening, as is found in asthma, as well as to loss of voice.