What is betaine?
Betaine, also called trimethylglycine, is a small organic osmolyte found in biological systems and used in cosmetics as a skin-conditioning ingredient. It should not be confused with cocamidopropyl betaine, which is a chemically distinct amphoteric surfactant and known contact allergen.[1,2]
How does betaine work?
Osmolytes participate in cellular responses to changes in water and solute balance. In cosmetic formulations, betaine is used to support Skin hydration.[2]
Can betaine reduce irritation from cleansing agents?
Two small controlled human exposure studies provide relevant evidence. In one study of 21 healthy subjects, betaine reduced irritation responses associated with tested sodium lauryl sulfate and cocamidopropyl betaine solutions under occlusive patch-test conditions. In another study of 28 healthy participants, soaps formulated with betaine were among the least irritating tested, but irritation differences were modest and increasing the betaine concentration did not produce a corresponding improvement across the concentrations examined. These are short-term detergent-exposure experiments, not clinical trials establishing treatment of eczema or rosacea. [1,3]
Does betaine prevent UV damage or reverse skin aging?
A laboratory study in organotypic rat epidermal keratinocyte cultures found that betaine influenced gene expression, including the differentiation marker keratin 2, under experimental conditions that included UVB exposure. These findings are mechanistic and hypothesis-generating so they do not demonstrate that topical betaine prevents photoaging or replaces sunscreen in humans. [2]
Is betaine appropriate for sensitive skin?
Betaine is an excellent addition in both leave-on and rinse-off sensitive skin formulas, particularly when a formulator is trying to mitigate surfactant irritation.
Evidence summary
The strongest directly applicable published evidence here concerns mitigation of detergent-induced irritation in small human exposure studies. Other proposed benefits—including specific barrier-protein changes, UV protection, and anti-aging effects—should remain qualified as laboratory findings until supported by appropriately designed human topical studies. [1–3]
References
[1] Nicander I, et al. (2003). The ability of betaine to reduce the irritating effects of detergents assessed visually, histologically and by bioengineering methods. Skin Research and Technology, 9, 50–58.
[2] Rauhala L, et al. (2016). The organic osmolyte betaine induces keratin 2 expression in rat epidermal keratinocytes—A genome-wide study in UVB irradiated organotypic 3D cultures. Toxicology in Vitro, 30, 462–475.
[3] Nicander I, Aberg P, Ollmar S. (2003). The use of different concentrations of betaine as a reducing irritation agent in soaps monitored visually and non-invasively. Skin Research and Technology, 9, 43–49.
