HSP overview:

What is Henoch-Schönlein purpura (HSP)?
Henoch-Schönlein purpura (say: hen-awk shern-line purr-purr-ah) causes blood vessels to get inflamed (irritated and swollen). This inflammation is called vasculitis. It usually affects the small blood vessels in the skin (capillaries). It can also affect blood vessels in the bowel and the kidneys. When the blood vessels get inflamed, they can bleed into the skin, causing a rash that is called purpura. The intestines and the kidneys may also bleed.
What causes HSP?
HSP is caused when a person's immune system doesn't fight an infection like it's supposed to. It occurs most often in the spring, usually after an upper respiratory infection, like a cold. HSP occurs most often in children from two to 11 years of age, but it can occur in anyone. Its exact cause is unknown. 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.
What are the symptoms of HSP?
HSP causes a skin rash, pain in the joints (such as the knees and ankles) and stomach pain. The rash looks like small bruises or small reddish-purple spots. It's usually on the buttocks, around the elbows and on the legs. HSP can also cause fever, nausea, vomiting and diarrhea. The symptoms usually last for about four to six weeks. If the blood vessels in the bowel and the kidneys get inflamed, HSP can make you bleed when you have a bowel movement or when you urinate. Serious kidney problems don't happen very often, but they can occur. In rare cases, an abnormal folding of the bowel called intussusception (say: in-tuh-suh-sep-shun) can occur. This makes a blockage in your intestines that may need surgery.
How is HSP treated?
There is no specific treatment for HSP. Medicines can help you feel better and treat an infection that may have triggered HSP. Fortunately, HSP usually gets better without any treatment. Anti-inflammatory medicines, such as ibuprofen (brand name: Advil) or naproxen (brand name: Alleve), can help the pain in your joints. Sometimes medicines like prednisone can help people with severe stomach pain.
What happens to people with HSP?
Most people do fine. Usually, HSP gets better on its own and doesn't cause lasting problems. About half of people who had HSP once will get it again. A few people will have kidney damage because of HSP. Your doctor may want to check urine samples several times after your HSP goes away to check for kidney problems. Be sure to see your doctor as many times as he or she tells you to.