What causes a birthmark?

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QUESTION: What causes a birthmark?

ANSWER: Red birthmarks (called “vascular”) are caused by an overgrowth of blood vessels. These vascular birthmarks are often temporary and simply go away after time. All other birthmarks (called “pigmented”) range from brown to black to bluish-gray. Their cause is not known, other than the fact that they represent a concentration of other-color melanin at the site. In most cases, treatment is not needed.

There’s no known method of preventing birthmarks in the first place, and people with prominent ones are encouraged to cover them generously with good quality sunscreen before going outside, to prevent possible complications (increased skin cancer risk, irritation, etc.). If your birthmark changes in color, size or texture, or if it becomes itchy, inflamed or bleeding, consult with your primary care provider right away.