A solar lentigo is a flat, pigmented spot on the skin caused by years of sun exposure. These spots, commonly called age spots or sun spots, range from light tan to dark brown or black and typically measure a few millimeters to several centimeters across. They are benign, but their appearance can overlap with more serious skin conditions, which is why understanding what they look like and how they behave matters.
Solar lentigines are extremely common. They appear in roughly 90% of light-skinned adults over age 60 and about 20% of light-skinned adults under 35. They cluster on areas that get the most sun: the face, the backs of the hands, the forearms, and the shoulders.
What Happens in the Skin
The spots form because of cumulative UV damage to the outermost layer of skin, the epidermis. Over years of sun exposure, UV radiation causes DNA damage in keratinocytes, the cells that make up most of the epidermis. These damaged keratinocytes begin overproducing signaling molecules that tell neighboring pigment-producing cells (melanocytes) to ramp up melanin output. The result is a localized patch of skin that contains roughly twice the melanin of the surrounding area.
What’s interesting is that the number of melanocytes in a solar lentigo isn’t dramatically higher than in normal skin. Instead, the skin’s surface architecture changes. The ridges where the epidermis connects to the deeper dermis become elongated and club-shaped, increasing the total surface area where melanocytes sit. Those melanocytes are also working harder, producing more pigment per cell. At the same time, the upper layers of the epidermis turn over more slowly, so the extra pigment lingers rather than shedding away. The combination of structural changes, increased melanin production, and slower skin cell turnover creates a persistent dark spot.
What Solar Lentigines Look Like
A typical solar lentigo is a flat macule, meaning it sits flush with the skin surface and you can’t feel a raised edge. Color ranges from skin-toned or light tan to dark brown or black. The borders are usually well defined and the pigmentation is even across the spot. They tend to appear in groups on sun-exposed areas rather than as isolated marks, which helps distinguish them from other pigmented lesions.
Size varies widely. Most are a few millimeters across, roughly the diameter of a pencil eraser, but some grow to several centimeters. They don’t itch, hurt, or bleed. If a spot starts doing any of those things, or if it changes noticeably in color, shape, or size, that warrants closer evaluation.
How to Tell Them Apart From Melanoma
The main reason solar lentigines get clinical attention is that they can look similar to lentigo maligna, a type of melanoma in situ that also appears on chronically sun-damaged skin of older adults. Lentigo maligna can be misdiagnosed as a harmless sun spot for years or even decades because it grows slowly and starts as a flat brown patch.
There are key differences. A solar lentigo typically has even pigmentation and a regular border. Lentigo maligna tends to show color variation within the same spot (mixing light brown, dark brown, and sometimes gray or black), asymmetric shape, and irregular or blurry borders. As lentigo maligna progresses, it may develop skip areas where the color appears patchy or noncontiguous. If the lesion becomes invasive, you might feel a raised or firm component within the spot. Advanced lesions can cause pain, burning, itching, or bleeding, none of which occur with a benign sun spot.
Dermatologists use a magnifying tool called a dermoscope to look more closely. Under dermoscopy, a solar lentigo shows a regular, honeycomb-like pattern. Lentigo maligna shows asymmetric pigment around hair follicle openings, diamond-shaped (rhomboidal) structures, and scattered gray dots. These patterns help guide the decision about whether a biopsy is needed, but even experienced dermatologists find the distinction challenging in early cases.
Treatment Options
Solar lentigines don’t require treatment for health reasons. Most people who seek treatment do so for cosmetic reasons. Options fall into two categories: topical creams and in-office procedures.
Topical Treatments
The best-studied topical approach combines a skin-lightening agent with a retinoid, which speeds up skin cell turnover. A combination of mequinol (a lightening compound) and tretinoin (a prescription retinoid) achieved clinical success rates of 52% to over 75% for spots on the arms and 56% to over 80% for spots on the face, depending on the study. Higher success rates on the face likely reflect the thinner skin there, which responds more readily to topical treatments.
Hydroquinone, another lightening agent, is often combined with tretinoin and a mild steroid. A triple-combination cream containing 4% hydroquinone, 0.05% tretinoin, and a low-dose steroid has been shown to be effective and safe for resolving solar lentigines. A simpler combination of hydroquinone 5% with tretinoin and a steroid was about 50% effective at reducing spots. Adapalene gel, a retinoid available over the counter at lower strengths, lightened spots in about 57% to 59% of patients.
These treatments take weeks to months, and results are gradual. The spots fade rather than disappear overnight. Skin irritation, dryness, and increased sun sensitivity are common side effects of retinoids, so consistent sunscreen use during treatment is important.
In-Office Procedures
For faster results, dermatologists offer cryotherapy (freezing the spot with liquid nitrogen) and laser treatments. Cryotherapy works by destroying the pigmented cells, causing the spot to crust over and peel off over one to two weeks. It’s quick and inexpensive but carries a risk of leaving a lighter or darker mark where the spot was, especially on darker skin tones.
Laser treatments use targeted light energy to break up melanin pigment. These tend to offer more precise results and a lower risk of uneven pigmentation compared to cryotherapy. Multiple sessions may be needed. Chemical peels, which remove the outer layers of skin, are another option, though they treat the entire area rather than targeting individual spots.
Preventing New Spots
Because solar lentigines result from cumulative UV damage, the most effective prevention is consistent sun protection. A study that tracked pigmentation changes over time found that daily use of an SPF 30 cream on one hand prevented the seasonal darkening and formation of new spots compared to the untreated hand. The key word is daily: sporadic sunscreen use before beach trips does far less than routine application as part of a morning skincare routine.
Protective clothing, wide-brimmed hats, and avoiding peak UV hours (roughly 10 a.m. to 4 p.m.) all reduce the UV load on your skin. Sun protection won’t erase existing spots, but it slows the formation of new ones and helps topical treatments work better by preventing ongoing UV-driven melanin production.
Monitoring Existing Spots
Once you have solar lentigines, the practical task is keeping an eye on them. A stable spot that stays the same color, shape, and size over time is almost certainly benign. The changes worth noting are the same ones that apply to any pigmented lesion: a spot that becomes asymmetric, develops uneven color (especially new gray or black tones), grows noticeably, or develops an irregular border. A spot that starts to itch, bleed, or feel raised deserves prompt evaluation.
People with many solar lentigines are, by definition, people with significant cumulative sun damage. That sun damage also raises the overall risk of skin cancer, so regular full-body skin checks are a reasonable habit regardless of whether any individual spot looks concerning.