Moles are very common. Most people have between 10 and 40 moles on their body. They may be pink, tan, brown, or a color similar the person’s normal skin tone.

Moles can be flat or raised. Flat moles are called junctional nevi and raised moles are called compound nevi.

Moles are usually round or oval and smaller than a pencil eraser. They may be present at birth or may appear later on—usually before age 40.

People who have dark skin tend to have dark moles. Moles may darken during pregnancy or after sun exposure. Moles tend to fade away in older people.

Melanocytes produce melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes produce more pigment, causing the skin to tan, or darken. Sometimes, clusters of melanocytes and surrounding tissue form noncancerous growths called moles. (A mole is also called a nevus, or the plural, nevi.)

A halo nevus occurs when the skin surrounding a mole loses its pigmentation or color. This is benign and often the central mole and white ring will disappear with time. Halo nevi are most common in children and teenagers.

Most moles are harmless and do not require treatment. When moles are surgically removed, they normally do not return.

Everyone should perform a monthly skin self-exam. This is particularly important if you have many moles on your body.

Use a body mole map to keep an inventory of the number moles, their location and appearance. You should make an appointment to see your doctor if you notice a new mole, a change in the size, shape or color of a mole, or find another suspicious skin lesion.

Avoiding sun exposure and using a sunscreen regularly are two basic steps to help prevent moles from developing.