Impetigo: A contagious skin infection, mostly in kids, that starts with red sores that ooze and form a yellow-brown crust. Vasculitis: Inflammation of blood vessels, sometimes related to autoimmune diseases. It can lead to red or purple spots on the skin. Hemangiomas: These are benign (non-cancerous) growths made up of blood vessels—usually appear as red or purple birthmarks. When to...