Slide show: Common birthmarks

Contrary to their name, birthmarks aren't always present at birth. Some, such as a strawberry hemangioma, develop weeks later. And though most are permanent, a few types of birthmarks fade as the child grows.

Most birthmarks are harmless, but some may require treatment for cosmetic reasons or because of rapid growth. Still others may be a sign of an underlying disease. Take this visual tour of cafe au lait spot, port-wine stain and other common birthmarks and find out when your child might need to see a doctor.

As the name implies, these permanent birthmarks are light and coffee colored. Cafe au lait (ka-FAY oh LAY) birthmarks are very common, and they can occur anywhere on the body. Usually, no treatment is needed.

A single cafe au lait spot or a pair of spots is common with this birthmark. Multiple birthmarks of this type, however, occur in a genetic disorder called neurofibromatosis. If your child has more than six cafe au lait spots, ask your doctor whether further evaluation is warranted.

Present at birth, a congenital nevus is a large, dark-colored mole that typically appears on the scalp or trunk of the body. It can range in size from less than 1 centimeter to 20 centimeters across, covering large areas.

Children with a congenital nevus — especially those with a large-sized nevus — are at an increased risk of developing skin cancer as adults. If your child has this type of birthmark, consult your doctor so that he or she can check for skin changes.

Also called mongolian blue spot, this large, blue-gray birthmark sometimes resembles a bruise. It's more common in darker-skinned babies, especially those of Asian heritage, appearing on the lower back and, less commonly, on the buttocks and legs. This birthmark may disappear later in childhood and requires no treatment.

A port-wine stain is a vascular malformation of capillary blood vessels in the deeper layers of the skin. It typically starts out pink, but as the child matures, turns darker red or purple. Most often, a port-wine stain appears on the face and neck, but it can affect other areas of the body. The size of a port-wine stain can vary from very small to quite large.

This lesion is a permanent birthmark, which doesn't decrease in size over time. In fact, it usually develops an irregular, pebbled surface and some swelling as the child grows. These physical changes of the port-wine stain, along with its cosmetic appearance, can cause both medical problems and emotional stress for the child. Laser therapy is the usual treatment of choice. Most port-wine stains aren't associated with other conditions. Some, however, are associated with Sturge-Weber syndrome and Klippel-Trenaunay syndrome and require regular medical evaluation.

Sometimes affectionately called stork bites or angel kisses, salmon patches are reddish or pink patches that are often found above the hairline at the back of the neck, on the eyelids or between the eyes (glabellar nevi). These marks are caused by collections of capillary blood vessels close to the skin. Salmon patches on the forehead, eyelids or between the eyes usually fade with time. Those on the nap of the neck usually don't fade but are covered by hair. Salmon patches don't require any type of treatment.

The hemangioma is the most common benign growth in infants. It's a collection of small blood vessels that grow rapidly in the skin during fetal development. This pink birthmark grows during the first year of life and then recedes over time. By age 10, a child who had a hemangioma in infancy usually retains little or no visible trace of the growth. Hemangiomas can be located anywhere on the body.

Medical treatment isn't typically required, but fast-growing hemangiomas sometimes require medication or laser treatments. Problems do occasionally arise if the growth is near the eye (difficulty with vision), in the throat (difficulty breathing), or near the mouth or groin (difficulty with feeding or elimination). Also, if a child has three or more hemangiomas on the skin, evaluation is recommended to search for internal hemangiomas, which occasionally occur.