Birthmarks occur where there is an over-abundance of a particular component of normal skin such as tiny blood vessels (capillaries) or pigment cells. The cause of this local condition is unknown.

The flat, pink birthmarks commonly seen on the forehead, eyelids, back of the neck, and above the bridge of the nose are called capillary hemangiomas, alsoknown as “stork bites” or “salmon patches.” These are seen in about 50 percent of newborns. Eyelid patches will disappear by three to six months of age, while those on the neck will fade but may last for years.

Areas of dark or bluish gray pigmentation known as Mongolian spots are common on the low back and buttocks of dark-skinned newborns, although these marks may be found in all racial and ethnic groups. These marks vary greatly in size and shape and usually disappear by two to three years of age.

A more permanent type of birthmark is the café and bait spot, a light brown flat patch that can occur any-where on the body. While some are present at birth, others may appear later in life. While these markings are benign, the presence of six or more of them measuring more than 15 mm (about 5/8 inch) in diameter may indicate a more serious problem known as neurofibromatosis.

One or more dark brown, black, or blue-black spots known as nevi, which contain large numbers of pigmented cells, may be seen at birth in about one in one hundred Caucasian infants. While the vast majority of these spots never cause any trouble, on rare occasion (usually in adolescence or even later in adulthood), one or more may transform into a dangerous type of skin cancer called a malignant melanoma. You should be-come familiar with the appearance of arty nevi on your child’s skin and watch in particular for any of the following warning signs: significant change in size; crusting, oozing, or bleeding; the development of an irregular border or color pattern; and change from a flat to a raised or rough contour. Should any of these changes develop, ask your child’s doctor or a dermatologist to ex-amine the area.

A more troublesome (but also uncommon) birthmark is the giant pigmented nevus, an irregular dark brown patch over four inches in diameter. If this covers a large area of the lower trunk, it is called the “bathing trunk nevus.” At a microscopic level this is structurally similar to the common moles (or juncfinevi), which become more common and widely spread over the skin later in life. Unfortunately, giant pigmenevi are much more likely than the smaller conge pigmented nevi to transform into malign melanomas. This change can occur during infancy any time later in life. For this reason a consultation with a dermatologist or plastic surgeon may be recommended an early age.