Niacinamide

Measured on: facial hyperpigmentation and skin lightness versus vehicle, computer image analysis and visual grading of high-resolution facial images.

The vehicle-controlled clinical arms are in Hakozaki et al. 2002: 18 Japanese women with facial hyperpigmentation using 5% niacinamide moisturiser against its vehicle in a paired split-face design, plus 120 women in a facial-tanning study on vehicle, sunscreen, or 2% niacinamide with sunscreen. The paper reports that niacinamide significantly decreased hyperpigmentation and increased skin lightness compared with vehicle after 4 weeks of use, so 4 weeks is the earliest measured separation and the end of the wait, not the start of it. Improvement continues past that point: the 12-week 5% split-face study in 50 women takes facial images at 4-week intervals and adds fine lines, red blotchiness, sallowness and elasticity to the list, so ageing endpoints are a longer wait than pigment. Caveats are about confidence, not timing - the pigment panel was 18 people and single-ethnicity, both trials are Procter & Gamble work, and image-analysed spot area is not clinical melasma grading. Consumer products at 4-5% match the trial concentration, which is unusual.

Hakozaki et al., Br J Dermatol 2002;147(1):20-31, 'The effect of niacinamide on reducing cutaneous pigmentation and suppression of melanosome transfer', PMID:12100180 - abstract read: significance versus vehicle 'after 4 weeks of use'. Bissett et al., Dermatol Surg 2005;31(7 Pt 2):860-5, PMID:16029679 (5% niacinamide versus vehicle, split-face, 12 weeks, images at 4-week intervals) for the endpoints that keep improving after week 4.