The exact cause of HSP is unknown. It is believed to be a disorder of the immune system. It may be triggered by bacterial or viral infections, certain medications, vaccines, or perhaps even insect bites. HSP frequently occurs in the spring, often after a respiratory infection. It is not contagious.
A risk factor is something that increases your chance of getting a disease or condition. Risk factors for HSP include:
- Recent upper respiratory illness, such as a cold
- Age: 2 to 11
- Recent exposure to vaccines, chemicals, cold weather, or insect bites
- Sex: male children are twice as likely as females to develop the disease; the risk is equal in adults.