Proline - The Dermatology Review




Proline is an amino acid that is primarily used in anti-aging skin care products because of its ability to improve skin elasticity, increase collagen production, and promote skin repair and regeneration.


Proline is an amino acid that is used as a building block in the production of proteins. It contains an α-amino group, an α-carboxylic acid group, and a side chain pyrrolidine. Proline is a non-essential amino acid, which means that the human body can synthesize it from the non-essential amino acid L-glutamate. In addition to use in skin care products, proline is often used in pharmaceuticals and biotechnological applications because it functions as an osmoprotectant.


In cosmetics and personal care products, proline primarily functions as an anti-aging ingredient because of its ability to improve skin elasticity, increase collagen production, and promote skin repair and regeneration.

After topical application, proline and other amino acids can effectively penetrate the skin because they have an average molecular weight of 110 Daltons. This is well under the 500 Dalton rule, which states that compounds above 500 Daltons have a much harder time penetrating into the skin.

Proline is often used in anti-aging skin care products because of its ability to reduce the appearance of fine lines and wrinkles. One factor that contributes to the formation of fine lines and wrinkles is decreased flexibility or elasticity of the stratum corneum (the uppermost layer of the skin). According to a publication in the European Journal of Dermatology, the elasticity of the stratum corneum has been shown to be regulated, at least in part, by the amounts and types of amino acids. This publication also reports that a study conducted on 126 Japanese female subjects found that topical application 1-carbamimidoyl-L-proline, a derivative of proline, significantly improved the appearance of crow’s feet lines. This suggests that proline and its derivatives are promising and useful ingredients for the improvement of wrinkles through the ability to enhance the elasticity of the stratum corneum.

Another major factor that contributes to the formation of lines and wrinkles is a decrease in the amount of collagen in the skin. The body produces less and less collagen with age. In fact, after the age of 20, a person produces about 1 percent less collagen in the skin each year. Moreover, environmental free radicals can degrade collagen proteins. The result is skin that becomes thinner and more fragile with age. Using ingredients that stimulate collagen production, such as proline, can help to maintain skin firmness and elasticity. Specifically, proline is a substrate that is necessary for collagen synthesis. Collagen has a triple helix structure composed of proline, hydroxyproline, and glycine.

Of all the amino acids that form collagen, proline’s effects on promoting skin health has probably been the most well-researched. It is well known that proline can help to repair damaged skin and promote wound healing due to its ability to support collagen synthesis. Collagen is necessary for wounds to heal properly because it gives structure and strength to the skin.


The safety of proline and the other alpha-amino acids has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. Due to the normal presence of proline in the body and its use as a direct food additive approved by the FDA, the Panel focused their review on dermal irritation and sensitization data. Dermal data on products containing proline indicated that this ingredient is not a dermal irritant or sensitizer. Thus, the Panel concluded that proline and the other alpha amino acids were safe as used in cosmetics and personal care products.

References: Wikipedia “Proline”, Eur J Dermatol 2013 Apr 1;23(2):195-201, Dr. Axe “Benefits of Proline + How to Get More in Your Diet” 2018, Cosmetics Info “Proline”


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