Niacinamide (vitamin B3) is scientifically supported as a topical treatment for age spots, also known as solar lentigines or hyperpigmentation. Several clinical studies have demonstrated that niacinamide can reduce the appearance of hyperpigmentation and even skin tone. Its primary mechanism involves the inhibition of melanosome transfer from melanocytes to keratinocytes, thereby decreasing the amount of melanin deposited in the skin. This effect helps to fade age spots, which are caused by localized increases in melanin due to sun exposure and aging.

For example, a pivotal randomized, double-blind clinical trial published in the British Journal of Dermatology (2002) showed that topical application of 5% niacinamide significantly reduced hyperpigmentation and improved overall skin lightness in Japanese women over 8 weeks. Additional studies have corroborated these findings, noting that niacinamide is well-tolerated and unlikely to cause the irritation sometimes seen with other skin-lightening agents like hydroquinone.

Given this body of evidence, niacinamide is widely used in dermatology and cosmetic formulations targeting age spots and uneven skin tone. While further research can always add nuance, the current scientific consensus supports niacinamide's efficacy and safety for treating age spots, justifying its inclusion in many over-the-counter skin care products.