A solar lentigo is a common, harmless patch of darkened skin that often develops on areas frequently exposed to the sun. These spots are widely known by other names, such as age spots, sun spots, or liver spots, though they have no relation to liver function. They result from the skin’s response to ultraviolet (UV) radiation and are prevalent in individuals over 40.
Understanding Solar Lentigines
Solar lentigines typically appear as flat, well-defined patches. Their shape can be round, oval, or irregular, and their color ranges from light tan to dark brown or even black. These spots vary in size, from a few millimeters to several centimeters, and may occasionally feel slightly scaly. While they can appear as single spots, they often present in groups on sun-exposed regions of the body.
These skin marks are most frequently found on the face, the backs of the hands, shoulders, arms, upper chest, and upper back. Solar lentigines are benign and pose no health threat. They are common, affecting over 20% of individuals over 35 and up to 90% of people over 60, especially those with fair skin.
The Role of Sun Exposure
The primary cause of solar lentigines is prolonged or repeated exposure to ultraviolet (UV) radiation from natural sunlight or tanning beds. This UV light triggers skin cells called melanocytes, which are responsible for producing pigment. When stimulated by UV radiation, melanocytes proliferate and produce an increased amount of melanin. This excess melanin then accumulates within the skin’s outer layer, forming the visible darkened patches.
Differentiating from Other Skin Marks
It is important to distinguish solar lentigines from freckles and moles, and particularly from more serious conditions like melanoma. Unlike freckles, which are often genetic and fade in winter, solar lentigines do not lighten with reduced sun exposure. Freckles are typically smaller, usually less than 3 millimeters, and often have less defined borders compared to solar lentigines. Moles, on the other hand, can be raised growths and vary more in appearance than the typically flat solar lentigines.
While solar lentigines are benign, their resemblance to melanoma, a form of skin cancer, necessitates careful monitoring. Healthcare professionals often use the “ABCDE” rule to help identify suspicious spots:
- Asymmetry refers to one half of the spot not matching the other.
- Border irregularity means the edges are ragged, notched, or blurred.
- Color variation indicates different shades of tan, brown, black, or even red, white, or blue within the same spot.
- Diameter considers spots larger than 6 millimeters, roughly the size of a pencil eraser, though melanomas can be smaller.
- Evolving highlights any change in size, shape, color, or elevation, or the development of new symptoms like itching or bleeding.
Any new or changing pigmented spot should be evaluated by a medical professional.
Management and Medical Consultation
For cosmetic reasons, several treatment options are available. Cryotherapy involves freezing the spots with liquid nitrogen, which effectively destroys the pigment-producing cells. Laser therapy uses targeted light energy to break down the excess pigmentation. Topical creams containing ingredients like retinoids or hydroquinone can also be used to lighten the spots over several months, though their effectiveness can vary. Cysteamine cream has also shown promise as an effective topical treatment.
Preventative measures minimize the development of new solar lentigines. This includes using a broad-spectrum sunscreen with an SPF of 30 or higher daily, even on cloudy days. Seeking shade during peak sun hours (10 AM to 4 PM) and wearing protective clothing like wide-brimmed hats and long sleeves are effective strategies. Avoiding tanning beds is another important step in prevention.