Henoch-Schönlein purpura (say "hen-awk shern-line purr-purr-ah") causes the blood vessels in your skin to get inflamed (irritated and swollen). This inflammation is called vasculitis. It can also affect blood vessels in the bowel and the kidneys. When the blood vessels in your skin get inflamed, they can bleed, causing a rash that is called purpura. The intestines and the kidneys may also bleed.

What causes HSP?

The exact cause of HSP is unknown. Doctors think HSP is caused when a person's immune system doesn't fight an infection like it's supposed to. It might be triggered by bacterial or viral infections, medicines, insect bites, vaccinations or exposure to chemicals or cold weather. You may catch an infection that caused someone's immune system to respond with HSP, but HSP itself isn't contagious. Doctors don't know how to prevent HSP yet.

HSP occurs most often in children from 2 to 11 years of age, but it can occur in anyone.