Why do we have birthmarks?(Ask Dr. Cory)

Why do we have birthmarks? I have one on my cheekbone.

Laurie Fields Aloha, Oregon Dear Laurie:

Birthmarks are on your body when you are born. That is why they are called "birthmarks." They appear in many colors, from light pink to dark brown or black. Doctors do not know what causes them, and no one has discovered a way to prevent them from appearing. Some people don't have any. Others have several. Birthmarks usually grow as the child grows and do not cause any problems.

However, large, dark brown or black birthmarks can be more serious. They may be as small…