Although it is unknown what causes most types of vasculitis, immune system abnormality, inflammation of blood vessels, and genetic factors appear to be somewhat important in the cause of the disease. Vasculitis can also be caused by an immune or allergic reaction in the vessel walls.
Allergic reaction: The hypersensitive response of the immune system of an allergic individual to a substance. When an allergen enters the body, it causes the body's immune system to develop an allergic reaction in a person with an allergy to it. This reaction can occur when the immune system attacks a normally harmless substance (the allergen). The immune system calls upon a protective antibody called immunoglobulin E or IgE to fight these invading substances.
An adverse reaction to a drug is any unintended effect of a drug, not including failure of the drug to work, abuse of the drug, or overdose of the drug. Adverse reactions to drugs include both drug allergy and drug intolerance. A drug allergy is caused by the immune system reacting to a drug. There are several different types of drug allergies that lead to allergic reactions. Reactions to drugs range from a mild, localized rash to serious effects on different