A study showed the synergistic effect of 4-hexylresorcinol (4-HR) with niacinamide in facilitating anti-melanogenic efficacy in-vitro and established the in-vivo efficacy and safety of the combination in a human trial.

It utilized Primary human epidermal melanocytes and 3D pigmented skin equivalents ministered with 4-HR, niacinamide, and their mixtures for their impact on pigmentation, which was followed by a randomized double-blind, split-face clinical study in Chinese subjects, where effects on skin tone, hyperpigmentation, fine lines and wrinkles, hydration, and skin firmness were evaluated during a 12-week study period.

The following observations were made-

• In-vitro tyrosinase enzyme activity studies demonstrated 4-HR to be one of the most potent tyrosinase inhibitors.
• 4-HR and niacinamide combination synergistically reduced the melanin production in cultured melanocytes and lightened the 3D skin equivalent model.
• 4-HR and niacinamide combination showed marked improvement in efficacy over niacinamide alone on hyperpigmentation spots as measured by L*, the visual appearance of fine lines and wrinkles in crows feet and perioral area and, skin firmness, with no product-related adverse events, in both in-vitro and the human trial.

Thus it was concluded that superior skin tone and anti-ageing benefits were furnished by 4-HR and niacinamide combination than niacinamide alone without any adverse events. 

This study highlighted that a product that affects multiple pathways of melanogenesis, inflammation, and ageing may be used as an alternative treatment option, to hydroquinone and retinoids, for hyperpigmentation and ageing.

Source- Shariff R, Du Y, Dutta M, Kumar SV, Thimmaiah S, Doraiswamy C, Kumari A, Kale V, Nair N, Zhang S, Joshi MM, Santhanam U, Qiu Q, Damodaran A. Superior even skin tone and anti-ageing benefit of a combination of 4-hexylresorcinol and niacinamide. Int J Cosmet Sci. 2021 Dec 27. doi: 10.1111/ics.12759. Epub ahead of print. PMID: 34958693.