PROLINE

📋 Quick facts

Description: PROLINE — amino acid, part of the skin natural moisturizing factor (NMF), supports collagen structure.

All Functions: amino acid, part of the skin natural moisturizing factor (NMF), supports collagen structure

Quick Facts:

• Category: humectant

Proven Benefits At A Glance:

• Proline is one of three amino acids that make up more than half of collagen, the most abundant protein in your body
• Collagen gives structure and strength to skin, bones, cartilage, and blood vessels
• Your body can make proline from other amino acids, but research suggests that supply may not always be enough
• When cells are making collagen, they rely heavily on converting another amino acid (glutamine) into proline rather than using proline directly from food

⚗️ Chemical Overview

L-proline is pyrrolidine in which the pro-S hydrogen at position 2 is substituted by a carboxylic acid group. L-Proline is the only one of the twenty DNA-encoded amino acids which has a secondary amino group alpha to the carboxyl group. It is an essential component of collagen and is important for proper functioning of joints and tendons. It also helps maintain and strengthen heart muscles. It has a role as a member of compatible osmolytes, a micronutrient, a nutraceutical, a mouse metabolite, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite and an algal metabolite. It is a L-alpha-amino acid, a glutamine family amino acid, a proline and a proteinogenic amino acid. It is a conjugate base of a L-prolinium. It is a conjugate acid of a L-prolinate. It is an enantiomer of a D-proline. It is a tautomer of a L-proline zwitterion. Proline is one of the twenty amino acids used in living organisms as the building blocks of proteins. Proline is sometimes called an imino acid, although the IUPAC definition of an imine requires a carbon-nitrogen double bond. Proline is a non-essential amino acid that is synthesized from glutamic acid. It is an essential component of collagen and is important for proper functioning of joints and tendons. L-Proline is a metabolite found in or produced by Escherichia coli (strain K12, MG1655).

Source(s): DrugBank, E. coli Metabolome Database (ECMDB), ChEBI, via PubChem

📊 Comedogenicity

🛡️ Safety rating

Safety tier is a starting heuristic from regulatory status and comedogenic rating, not a dermatological verdict — see our Terms for the full disclaimer. Research confidence reflects how many real cited studies back this ingredient, not the strength of their findings.

🌍 Regulatory Status

💧 Skin Type Compatibility

⚠️ Don’t Combine With

📚 Research & Evidence

🔬 The Science

Proline’s main claim to fame in skincare is its role in collagen. Collagen accounts for roughly one-third of all protein in the body and is the single most abundant protein overall (Amino Acids, 2018). Proline, glycine, and hydroxyproline together make up 57% of collagen’s amino acid composition, making proline a structural cornerstone of this critical protein (Amino Acids, 2018). Collagen is essential for maintaining the normal structure and strength of connective tissues, including skin, bones, cartilage, and blood vessels (Amino Acids, 2018). #1: Your body can synthesize proline on its own—specifically from the amino acid arginine (Amino Acids, 2018). However, recent research indicates that the amount your body makes may not be adequate for maximal collagen production (Amino Acids, 2018).

#2: The way cells actually obtain proline for collagen-making is more complex than simply absorbing it from your diet. When fibroblasts (the cells that synthesize collagen) have access to the amino acid glutamine, they primarily convert glutamine into proline rather than using proline directly from outside sources. Notably, when glutamine is absent, added proline becomes much more important for collagen biosynthesis (Cell Mol Life Sci, 2020). This suggests that proline availability does influence collagen production rates, but the cell’s preferred pathway involves converting glutamine—highlighting that collagen synthesis depends on a broader amino acid ecosystem, not proline alone. The sources provided do not contain evidence supporting any direct skincare benefits from topical or ingested proline, anti-aging claims, or specific efficacy percentages for cosmetic use.

📄 Related Research

Matched by search — not necessarily verified support for every statement above.

• Li P et al. (2018). Roles of dietary glycine, proline, and hydroxyproline in collagen synthesis and animal growth. Amino Acids.
• Karna E et al. (2020). Proline-dependent regulation of collagen metabolism. Cell Mol Life Sci.
• Hoyos D et al. (2022). The genotypes and phenotypes of missense mutations in the proline domain of the p53 protein. Cell Death Differ.
• Schwan WR (2022). Proline Transport and Growth Changes in Proline Transport Mutants of Staphylococcus aureus. Microorganisms.
• Mitsubuchi H et al. (2008). Inborn errors of proline metabolism. J Nutr.

🧴 Products Containing PROLINE

• BCL Kansosan Skincare Moisture Base AQ
• RETINOL RETINOL SKIN CREAM
• MyProtein Hair & body wash
• L’OREAL NORGE AS Excellence 10 Ekstra Lys Blond
• L’OREAL NORGE AS Excellence 5.5 Lys Mahognibrun
• L’OREAL NORGE AS Excellence 9 Meget Lys Blond
• L’OREAL NORGE AS Excellence 6 MørkeBlond
• Bioélixire Odżywka do włosów zniszczonych
• Elmiplant Skin Moisture
• Cella Lozione Dopobarba Bio
• L’OREAL NORGE AS Excellence 8.3 Lys Gyldenblond
• Les Cosmetiques Facial pieles sensibles spf30 sun ultimate
• Tío Nacho Tío Nacho Anti-Caida Engrosador
• L’OREAL NORGE AS Excellence 4.3 Golden Brown
• L’OREAL NORGE AS Excellence Creme Ultra 3.11 Ash Dark Brown
• L’OREAL NORGE AS Excellence Creme Ultra 4.11 Ash Brown
• Clinique Clinique Dramatically Different Lipstick Shaping Lip Colour, 44 Raspberry Glace
• REMEDY CALAZIME Skin Protectant Paste
• marc anthony argan shampoo
• Avant Skincare Gentle Rose Beautifying Face Exfoliant
• Pacifica Cosmic Hemp Balancing Face Wash
• BOBBI BROWN Soothing Cleansing Oil Face Cleanser
• Vitamasque Cranberry & Apple Limited Edition
• NIOD Multi-Molecular Hyaluronic Complex (MMHC2)
• The Ordinary The Ordinary Glycolic Acid 7% Toning Solution (Solução tonificante de ácido glicólico 7%)
• ordinary suncream
• dr groot shampoo
• boscia Cryosea Firming Icy-cold Cleanser
• Paul Mitchell Paul Mitchell Awapuhi Shampoo
• Mineral Fusion Revitalizing Eye Treatment
• collagen face mask
• OPLAPLEX Leave In – Numéro 5
• Sephora Beauty insider
• Phytoplex cream
• Olaplex No. 8 Bond Intense Moisture Mask
• FILORGA TIME-FILLER Crème Absolue Correction Rides
• Ole Henriksen Banana Bright+ Eye Crème
• Agnès b Croissance!
• Henkel, Diadermine Lift + Lissage immédiat Gel-Crème Sublime Regard
• lavera Straffende Nachtpflege