A skin lesion is an abnormal growth or patch of skin that doesn't look like the area nearby. Skin lesions can be divided into two categories: primary and secondary.

Primary skin lesions are variations in color or texture that may be present at birth, such as moles or birthmarks. They also may appear during a person's lifetime, such as warts, acne, or psoriasis, allergic reactions such as hives or sunburn.

Secondary skin lesions include changes in the skin caused by primary skin lesions, either as a natural progression or because of scratching or picking at the skin.

The major types of primary lesions are:

• Macule. A small, circular, flat spot less than a quarter of an inch wide. The color of a macule is different from nearby skin, and are usually brown, white, or red. Freckles and flat moles are considered macules. Macules bigger than an...