What is Sodium PCA?
PCA is the cosmetic ingredient term used for the cyclic organic compound known as 2-pyrrolidone-5-carboxylic acid. The sodium salt is a naturally occurring humectant in the stratum corneum at levels about 12% of the Natural Moisturizing Factor (1) corresponding to about 2% by weight in the stratum corneum (2). The sodium salts of PCA are among the most powerful humectants.
What are its benefits to the skin and how is it used it the cosmeceutical industry?
Sodium PCA is a humectant that has high water absorbing properties and binds moisture to cells, and hold several times its weight in water. It is also considered to be hygroscopic, which means that it has the ability to absorb moisture from the air.
Among its many functions is that it delivers moisture to the hair and skin, and is often seen as an emollient or humectant in hair conditioners and moisturizers. It is also used as an ingredient in shampoos, hair sprays, permanent waves, skin fresheners and other hair and skin care products.
A study wherein treatment with a cream containing 5% sodium-PCA also increased the water-holding capacity of isolated corneum compared with the cream base (3). The same cream was also more effective than a control product containing no humectant, and equally effective as a similar established product with urea as humectant, in reducing the skin dryness and flakiness.
Studies regarding the safety of sodium PCA was applied to the shaved trunk of each animal once a day for 14 days. Observations were made every day and for an additional 2 weeks following the last application. No irritation was observed at any of the concentrations tested (4). In another study, 5% aqueous Sodium PCA was applied to the abraded skin of 30 white female Hartley guinea pigs. Applications were made once a day for 3 days. A control group of guinea pigs was treated similarly with distilled water. SodiumPCA was non irritating to the skin (4). Sodium PCA was also tested for primary skin irritation using rabbits. Applications were made to both intact and abraded sites for 24 hours, and the sites were scored 24 and72 hours after application. Sodium PCA was classified as a non-irritant (5).
1 Jacobi O. Moisture regulation of the skin. Drug Cosmet Ind 1959; 84:732–812.
2 Laden K, Spitzer R. Identification of a natural moisturizing agent in skin. J Soc Cosmet Chem
3 Middleton JD, Roberts ME. Effect of a skin cream containing the sodium salt of pyrrolidone
carboxylic acid on dry and flaky skin. J Soc Cosmet Chem 1978; 29:201–205.
4 Ajinomoto Co., Inc. 1994b. Supplementary safety evaluations on animals. Technical Bulletin AJD-8002.
5 Usines Chimiques D’lvry-la-Bataille (UCIB). 1987. Comedogenic capacity ofpyrolidone carboxylate sol aquesuse 50%. Unpublished data submitted byBarnet Products Corp.
*more related studies: https://journals.sagepub.com/doi/pdf/10.1177/109158189901800206