What are the different types of birthmarks?

　　A birthmark is an abnormal proliferation of skin tissue during development, resulting in abnormalities in shape and color on the skin surface. It may be caused by increased melanin, blood vessel proliferation, or vascular malformations. Generally, birthmarks can be categorized into two main types: pigmented birthmarks and vascular birthmarks.

　　Pigmented birthmarks mainly include nevus of Ota, café-au-lait spots, and congenital melanocytic nevi. These types of birthmarks generally do not directly affect health, and some may gradually fade or even disappear with age. If they do not affect appearance or psychological well-being, usually no special treatment is required.

　　Vascular birthmarks mainly include port-wine stains and strawberry hemangiomas. They consist of blood vessels near the skin surface and are usually related to vascular clustering or developmental abnormalities. These birthmarks may grow gradually, potentially compressing surrounding tissues, affecting organ function, or even carrying a risk of rupture and bleeding. In such cases, it is recommended to consult a physician for evaluation and determine whether treatment is necessary.

　　In daily life, excessive friction or irritation to the area of the birthmark should be avoided. If abnormal changes occur in the birthmark, such as rapid enlargement or surface ulceration, prompt medical evaluation is advised.