Melatonin

Melatonin is a compelling dual anti-pollution and circadian repair active. In human skin explant studies, a combination of melatonin + carnosine + Helichrysum italicum extract reduced AhR expression by 96% following PAH and heavy metal mixture exposure — the most potent AhR downregulation result in the literature. AhR is the central mediator of pollution-induced skin damage; suppressing it by 96% would theoretically prevent the entire downstream cascade (CYP1A1, MMP-1, IL-6/IL-8). Additionally, evening blue light exposure suppresses melatonin-mediated nocturnal skin repair; topical melatonin in night creams can partially restore this repair signaling independently of endogenous systemic suppression. Best positioned in anti-pollution night creams at 0.1–0.5%, combined with carnosine and a botanical AhR antagonist.

Permitted in cosmetics; sold as dietary supplement in the US without restriction; topical cosmetic use permitted; no FDA concentration restrictions for cosmetic application; not a CIR-reviewed cosmetic ingredient as of current data