Port wine stains are a type of birthmark characterized by their reddish to purplish color, resembling the color of port wine. These birthmarks are caused by abnormal blood vessels near the surface of the skin. Port wine stains are usually present at birth and can vary in size and shape. While they are generally harmless, their appearance can be a source of concern for some individuals.

Port wine stains can occur anywhere on the body but are most commonly found on the face, neck, or limbs. The color of the stain may deepen over time, and the affected area may become thicker or develop a raised texture.