Henoch-Schonlein purpura is a form of vasculitis that causes small hemmorhages (purpura) beneath the surface of the skin that can be perceived by touch. It usually also causes joint pain and abdominal pain and, in rarer cases, damage to the kidneys. The symptoms can often be set off by an infection, but can also be set off by some types of antibiotics. Although it can affect adults, it is far more common in children. Some of the complicaitons of Henoch-Schonlein are blood in the stool and nausea from the abdominal pain.