Sunspots, medically termed solar lentigines, are a common form of hyperpigmentation that develops on the skin. They represent a clear sign of chronic exposure to ultraviolet (UV) radiation from the sun or tanning beds. These lesions result from an overproduction of melanin, the skin’s natural pigment, in response to accumulated sun damage over time. Although they are sometimes mistakenly called “liver spots” or “age spots,” sunspots have no connection to the liver’s function and are solely a dermatological manifestation of long-term UV insult.
The Defining Visual Characteristics
Sunspots present as flat patches of darkened skin, medically known as a macule. They are entirely smooth to the touch, which differentiates them from raised growths like moles. This flatness results from the excess melanin being contained within the epidermis, the skin’s outermost layer.
The coloration of a sunspot can vary widely, ranging from a light tan or yellowish-brown to a darker brown or near-black hue. The pigmentation within a single spot is generally uniform, lacking the multiple shades often seen in more concerning lesions.
Sunspots have distinct, well-defined borders, creating a clear demarcation between the hyperpigmented area and the surrounding normal skin. While the edges are sharp, the overall shape can be round, oval, or somewhat irregular, sometimes described as having a scalloped outline.
Sunspots often start as very small, pinhead-sized lesions, but they can slowly enlarge over time with continued UV exposure. They typically grow to be several millimeters in diameter, sometimes reaching up to one or two centimeters. Smaller lentigines may also merge, creating a larger, irregularly shaped patch of discoloration.
Where Sunspots Commonly Appear
The distribution of solar lentigines is directly tied to areas that receive the highest cumulative sun exposure. They are most frequently found on the head and neck, particularly the cheeks, temples, and the sides of the face, as these areas are often exposed to sunlight year-round.
The backs of the hands are another common site for sunspot development, as they are rarely covered and constantly exposed to UV radiation. Similarly, the forearms and shoulders frequently show these lesions, especially in individuals who spend significant time outdoors.
The upper chest (décolletage) is also highly susceptible to sun damage and sunspot formation. Other areas of chronic exposure, such as the upper back and lower legs, can also develop solar lentigines. Sunspots rarely appear on parts of the body that are consistently covered by clothing.
Distinguishing Sunspots from Other Marks
Differentiating sunspots from other pigmented marks, such as freckles, moles, and melasma, is a common point of confusion. Freckles (ephelides) are often mistaken for sunspots but are typically smaller and characterized by a temporary increase in melanin production following sun exposure.
A key difference is that freckles tend to lighten significantly or disappear during winter months when sun exposure is reduced. Sunspots, conversely, are caused by a localized proliferation of pigment-producing cells and remain present year-round, regardless of seasonal changes.
Moles (nevi) require distinction from sunspots. While some moles are flat, they represent a cluster of pigment cells, which often makes them raised and palpable. Unlike moles, which can appear anywhere, sunspots are strictly limited to sun-exposed areas. Monitoring moles for changes in asymmetry, border, color, diameter, or evolution is important, as sunspots are benign and do not carry the same risk of malignancy.
Melasma is another form of hyperpigmentation, but it differs significantly in appearance and cause. It typically presents as larger, more diffuse, and patchy areas of gray-brown discoloration, rather than the discrete spots characteristic of solar lentigines. Melasma patches often appear symmetrically on both sides of the face, commonly across the cheeks, forehead, and upper lip. Melasma is frequently linked to hormonal factors, such as pregnancy or oral contraceptive use, in addition to sun exposure, distinguishing it from the purely UV-driven development of sunspots.