What causes age spots and can you prevent them?

Chronic sun exposure is the primary cause of age spots. They are a sign of photodamage to the skin and typically appear from the age of thirty onward on areas that receive a lot of sun, such as the hands, forearms and face. The more hours of sun exposure a person has accumulated, the greater the likelihood of developing these spots.

Deeper in the skin, a combination of processes is at play. Melanin, the brown pigment that provides colour, is produced by specialised cells (melanocytes) via an enzyme called tyrosinase. As a person ages, the total number of active melanocytes decreases, but the remaining cells become more active and distribute pigment more unevenly. It has also been established that the deepest skin cells (keratinocytes) within the spots divide more rapidly while the overlying cells are replaced more slowly, leading to an accumulation of melanin. Notably, the genes that regulate melanin pigment are not additionally activated in this process: it is therefore more a matter of disrupted cell turnover than an overactive pigment system.

A contributing factor is chronic low-grade inflammation. UVB radiation and cellular ageing together increase the production of an inflammatory receptor in keratinocytes, which stimulates the dendrites of melanocytes to grow and thereby causes additional melanin deposition. The protein E-cadherin also plays a role: this protein normally regulates communication between skin cells, but is present in reduced amounts in age spots, causing more melanin-promoting substances to be released. The latter has been demonstrated in cell culture experiments and has not yet been confirmed in clinical studies in humans.

Prevention starts with sun protection. Because chronic sun exposure is the clearest and causal cause, consistent use of sunscreen and avoiding prolonged exposure is the most logical prevention strategy, although the studies provided include no large trials that directly measure this preventive effect. For the treatment of existing spots, modern short-pulse lasers, applied with targeted focus on pigment, are the best-supported option. They produce clear improvement with few side effects, although those results are based primarily on case reports and literature reviews rather than large randomised trials.

Dietary supplements and plant-based extracts have also been studied, but the evidence for them is still very limited. In a small study, daily intake of blood orange extract (100 mg per day, 15 days) substantially reduced the increase in melanin following UV exposure. This is a preliminary finding from a single study of limited size. Extract from the fruit of a rose species (Rosa multiflora) increased the protein E-cadherin in cell culture experiments, which could theoretically counteract spot formation, but this is purely laboratory research. Neither option is ready for a concrete recommendation.