What causes HSP?
The exact cause of HSP is unknown. Doctors think HSP happens 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 is more common in boys than in girls. It most commonly affects children 2 years to 11 years of age, but it may affect people of any age.
Written by familydoctor.org editorial staff