Because the red birthmark is caused by vascular malformation, and the disease occurs in epidermis and dermis, the affected part of the patient may often be rubbed or scratched, thus causing ulceration and bleeding, especially in summer, because of the hot weather, it is easy to sweat, and the patient will itch when sitting on the skin. Because of frequent scratching, it leads to a lot of bleeding for a long time. The danger of red birthmark after ulceration and bleeding is easy to be infected.