Sunspots, medically known as solar lentigines, are a common form of hyperpigmentation resulting from cumulative ultraviolet (UV) radiation exposure. These spots are harmless signs of photoaging that accumulate throughout a person’s life. Although often called “age spots” or “liver spots,” their true cause is chronic sun exposure, not age or liver function.
Defining the Visual Characteristics
Sunspots present as distinct, flat patches of darkened skin that range significantly in color. The hue varies from a light tan or yellowish-brown shade to a much darker brown or even black. This pigmentation occurs due to an increased localized concentration of melanin, the natural pigment that gives skin its color.
The texture of a solar lentigo is smooth and level with the surrounding skin. They typically feature a well-defined border, though their shape can be irregular—often oval, round, or somewhat jagged, sometimes described as having a “moth-eaten” outline. Sunspots can start small, just a few millimeters across, but they can expand over time to reach several centimeters in diameter.
Common Locations and Underlying Cause
These pigmented spots develop almost exclusively on areas of the body that have received the most cumulative sun exposure. This includes the face, the backs of the hands, the forearms, shoulders, and the upper chest or back. Their appearance in these specific locations confirms they are a direct consequence of long-term UV light damage.
The underlying mechanism involves the skin’s pigment-producing cells, called melanocytes, which are stimulated by UV radiation. This exposure triggers a local proliferation of these cells and an excessive production of melanin, which then accumulates within the skin’s surface layers. Unlike a temporary tan, this localized overproduction creates a persistent, concentrated patch of darkness that does not fade without intervention.
Distinguishing Sunspots from Other Blemishes
It is important to differentiate solar lentigines from other common skin marks. Sunspots are often mistaken for freckles (ephelides), but true freckles tend to darken with sun exposure in the summer and then lighten or fade significantly during the winter months. Sunspots, on the other hand, are permanent and persist indefinitely unless actively treated.
Another type of growth, seborrheic keratosis, can sometimes develop within a sunspot, which will introduce a change in texture. This makes the spot feel waxy, thickened, or raised, unlike the purely flat solar lentigo. The most serious distinction involves ruling out melanoma, a form of skin cancer that can mimic a benign sunspot.
The ABCDE Method
To help identify potentially dangerous lesions, medical professionals recommend the ABCDE method of detection:
- Asymmetry
- Irregular Border
- Varied Coloration
- Diameter larger than a pencil eraser (6mm)
- Evolving size, shape, or symptoms like bleeding or itching
A typical sunspot will be symmetrical, have a clear border, and maintain a consistent color, without changing or evolving over time. Any mark exhibiting the signs of the ABCDE rule should be examined promptly by a dermatologist.
Addressing Management and Prevention
While sunspots are medically harmless, many people seek to manage their appearance for cosmetic reasons. The most effective approach to both management and prevention is rigorous sun protection, which limits the UV damage that causes the spots to form and darken. This involves wearing broad-spectrum sunscreen with an SPF of 30 or higher every day.
Protective clothing, such as wide-brimmed hats and tightly woven fabrics, should be used to shield the skin. Direct sun exposure should also be avoided during peak hours, typically between 10 AM and 4 PM.
Treatment Options
For existing spots, topical treatments like prescription hydroquinone or retinoids can slowly lighten the pigmentation over time. More immediate reduction can be achieved through professional procedures, including cryotherapy, which freezes the spot, or various laser treatments that target and break down the excess melanin. These options should always be discussed with a skin specialist.