Birthmarks: Who gets and causes
Who gets birthmarks?
Birthmarks are common. Research shows that about 10% of babies are born with a type of birthmark known as a hemangioma (he-man-gio-ma).
Fortunately, most hemangiomas go away on their own by the time a child is 10 years old. Many disappear sooner.
Babies may be more likely to have a hemangioma if they are:
Less than 5-1/2 pounds at birth
Born with a sibling (twin, triplet, etc.)
Birthmarks that cause a brown mark on the skin, such as moles and café-au-lait (café-oh-lay) spots, are also common. About 1 in 100 babies has a small mole. Larger moles are less common. Babies of all races can have a mole.
A Mongolian spot is another common birthmark. Asians are most likely to be born with one of these spots. Mongolian spots are less common in other races.
While some babies have a greater risk of developing certain birthmarks, there’s no way to know whether a baby will have a birthmark.
What causes a birthmark?
Different types of birthmarks have different causes. Before explaining these causes, it’s important to put some superstitions to rest.
Birthmarks don’t form because a pregnant woman ignores a food craving, touches her belly while worried, or eats certain foods. These are myths.
We still don’t know exactly why birthmarks develop, but here’s what scientists have learned so far.
Sisters with salmon patches
Sometimes, a birthmark runs in a family like this salmon patch, which has nearly faded on the older sister.
The cause varies with the type of birthmark. Some birthmarks form when blood vessels do not form properly. This can cause your baby to have one of the following birthmarks:
Other birthmarks appear when cells that give our skin color, melanocytes (meh-lan-oh-cites), clump together. That’s why newborns develop moles or café-au-lait spots.
A nevus sebaceous (knee-vus seh-bay-ceous) develops when parts of the skin overgrow.
You cannot prevent these things from happening by satisfying every food craving or keeping your hands off your belly while worried. So, it’s okay to ignore that desire for a turkey sandwich at 2:00 a.m.
Related AAD resources
Barnhill RG and Rabinovitz H. “Benign melanocytic neoplasms.” In: Bolognia JL, et al. Dermatology. (second edition). Mosby Elsevier, Spain, 2008:1713,1720-3.
Enjolras O. “Vascular malformations.” In: Bolognia JL, et al. Dermatology. (second edition). Mosby Elsevier, Spain, 2008:1582-5.
Garzon MC “Infantile hemangiomas.” In: Bolognia JL, et al. Dermatology. (second edition). Mosby Elsevier, Spain, 2008:1567-8.
Leffell DJ. Total skin: The definitive guide to whole skin care for life.” Hyperion, United States of America, 2000:286.
Nouri K, Patel AR, et al. “Mohs micrographic surgery.” In: Nouri K. Skin Cancer. The McGraw-Hill Companies, Inc., China, 2008:482-490.
McCalmont TH. “Adnexal neoplasms.” In: Bolognia JL, et al. Dermatology. (second edition). Mosby Elsevier, Spain, 2008:1695-6.