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.
What Are the Symptoms of an Allergy? An allergy occurs when the bodyâs immune system sees a substance as harmful and overreacts to it. The symptoms that result are an allergic reaction. The substances that cause allergic reactions are allergens. Allergens can get into your body many ways to cause an allergic reaction. 1  You can inhale allergens into your nose and your lungs. 2  You can ingest allergens by mouth. 3  Your body can have allergens injected into it.  Your skin can absorb allergens.