Vitamin C (ascorbate) is widely used in topical formulations for the treatment and prevention of age spots (also known as solar lentigines or hyperpigmentation) and is supported by a moderate body of scientific evidence. The rationale stems from Vitamin C's ability to inhibit melanin synthesis. Mechanistically, Vitamin C acts as a reducing agent that interferes with the action of tyrosinase, a key enzyme in the melanin biosynthetic pathway, thereby reducing melanin production. This effect can lighten hyperpigmented areas and even skin tone.

Clinical studies have demonstrated that topical application of Vitamin C can lead to improvements in hyperpigmentation, including age spots. For instance, several double-blind, placebo-controlled trials have shown that Vitamin C, especially in combination with other agents such as Vitamin E or ferulic acid, reduces the appearance of age spots and improves overall skin brightness. However, the degree of improvement varies between individuals and depends on formulation stability and concentration, as Vitamin C is unstable and can degrade upon exposure to light and air.

While the evidence is not as robust as that for some prescription agents (e.g., hydroquinone), Vitamin C is considered a safe and well-tolerated option for addressing age spots and is commonly included in dermatological and cosmetic regimens for this purpose.