Cumulative Exposure · Photoageing · CityLink Mall
Sun spots are not caused by getting older. They are the accumulated record of ultraviolet exposure, and they appear on the face, hands and forearms because those are the surfaces that have taken it — which is why they arrive earlier in Singapore than in most places people compare themselves to.
A solar lentigo differs from most facial pigmentation in that the melanocyte population itself has increased. Repeated ultraviolet exposure over years stimulates melanocyte proliferation in localised patches of epidermis, and the rete ridges — the downward folds where epidermis meets dermis — elongate in a characteristic club-shaped pattern, carrying additional pigment-producing cells with them. The result is a lesion with both more melanocytes and more melanin per cell. That is why it does not fade over the winter the way a freckle does, and why it stays where it is indefinitely.
The distribution tells the story without the patient having to. Lentigines occupy the cheekbones, temples, nose, the dorsum of the hands, the forearms and the upper chest. They are absent under a watch strap and sparse in the shade of the jawline. In Singapore, where ultraviolet index runs high year-round and there is no seasonal reprieve, the exposure accumulates faster than the timelines quoted in European or North American material — which is why patients here commonly see their first lentigines in their thirties rather than their fifties and reasonably conclude that something is wrong.
Two things determine how a lentigo responds to treatment. The first is that its melanin is epidermal and reasonably concentrated, which makes it a clean target for pigment-selective laser — the pigment absorbs energy, fragments, and is cleared over subsequent weeks. The second is that the increased melanocyte population remains in place after the visible pigment has gone. The lesion has been emptied, not removed. If the exposure that created it continues unabated, it refills.
It is also worth being precise about what a lentigo is not. It is not a seborrhoeic keratosis, which is raised and can be felt with a fingertip. It is not melasma, which is symmetrical, ill-defined and hormonally influenced. And on rare occasions a pigmented macule on chronically sun-exposed skin is not benign at all. Any lesion that has been enlarging, has an irregular or notched border, contains more than one colour, or looks different from every other spot on the same face warrants dermatological assessment before any laser is aimed at it.
The Distinction
Several unrelated conditions produce brown marks on sun-exposed skin, and they respond very differently to the same laser. The one below that matters most clinically is the third, because it is the reason a lesion is examined properly before it is treated rather than after.
A lentigo is not a sign of age. It is a sign of exposure — which is why two people of the same age can have completely different faces.
Management
Lentigines respond well to pigment-selective treatment, and this is genuinely one of the more satisfying things done in the clinic. A picosecond laser or an appropriately chosen pigment platform fragments the melanin within the lesion; over the following days the treated spot darkens, crusts faintly and lifts, and the skin beneath comes back matched to its surroundings. Most lesions need one or two passes rather than a course, and the R2 Glow protocol exists for the more diffuse background of photodamage that usually accompanies them.
The caveat is skin type. In Fitzpatrick III to V skin the surrounding epidermis also contains melanin, so energy intended for the lesion is partly absorbed by the skin around it — and excessive fluence produces post-inflammatory hyperpigmentation that is darker and more troublesome than the original spot. Conservative settings, test spots where the picture is uncertain, and adequate intervals between sessions are how that is avoided. Treatment that goes too hard on Asian skin trades one pigmented mark for a larger one.
What determines the long-term result is what happens afterward. The melanocyte population that generated the lentigo is still present, and continued ultraviolet exposure will repopulate the site — often within a year or two. Daily broad-spectrum photoprotection is therefore not an afterthought but the maintenance plan itself. The same logic applies to the hands and forearms, where photodamage is usually well ahead of the face and where hand rejuvenation addresses the volume loss and vein prominence that accompany it.
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