Serine
L-Serine is a non-essential amino acid and a component of the natural moisturizing factor (NMF) of the stratum corneum. Holds water in the epidermis. Often listed alongside glycine, alanine, and histidine in amino-acid complexes. Pregnancy-safe.
Evidence by route
Topical application
A natural NMF component of the stratum corneum. Humectant activity through osmotic water binding is physiologically established. Standalone effect of a single amino acid is moderate; synergy is higher in amino-acid complexes.
- Rawlings AV, Harding CR. Moisturization and skin barrier function. Dermatol Ther 2004;17(suppl 1):43-48. PMID 14728698
- Verdier-Sevrain S et al. Skin hydration: a review on its molecular mechanisms. J Cosmet Dermatol 2007;6:75-82. PMID 17524122
How to read tiers A–F
- BLimited evidence. One RCT or several controlled studies with limitations
Tolerability and safety
- Irritation potential
- Low
- Allergen risk
- Low
- Pregnancy
- Safe
- Suitable for
- Normal, Dry, Combination, Oily, Sensitive
About this ingredient
Serine is a non-essential amino acid with a hydroxyl side chain. The body synthesizes it from 3-phosphoglycerate, and it participates in phospholipids, sphingolipids, and neurotransmitter formation. In the skin, serine is part of the natural moisturizing factor (NMF) of the stratum corneum – together with glycine, alanine, histidine, arginine, threonine, lysine, and pyrrolidone carboxylic acid (PCA). NMF holds up to 30% of the water in the stratum corneum. INCI: Serine. In cosmetics, L-Serine works as a humectant and barrier-rebuilding component. At the stratum-corneum level serine: 1. Binds water molecules through its hydroxyl and amino-carboxyl groups. 2. Supports the osmotic balance of corneocytes. 3. Acts as a substrate for stratum-corneum ceramide synthesis through the sphingolipid pathway (sphingosine, dihydrosphingosine). In dry and aging skin, NMF concentration decreases – topping up with serine and other amino acids theoretically restores hydration capacity. This is a working model, but clinical RCTs with direct mono-amino-acid effect on skin are scarce – usually the studies look at complete amino-acid complexes alongside other actives. Use. Concentrations are 0.1-2% in serums, creams, and toners. It is often combined with glycerin, hyaluronic acid, and betaine for humectant synergy. Compatible with all actives and pH ranges. Pregnancy safety. Topical use is safe. Systemic absorption through intact skin is minimal. Serine is a natural metabolite synthesized by the body, so there are no toxic effects. Safe in lactation as well. Skin tolerance. Very low irritation and allergen potential. Non-comedogenic. Suitable for sensitive, pediatric, and atopic skin.
Frequently asked questions
Is Serine safe during pregnancy?
Serine is considered safe during pregnancy at typical cosmetic concentrations. Systemic absorption through the skin is minimal.
What skin types is Serine for?
Serine suits: normal, dry, combination, oily, sensitive.
What is Serine and what does it do in cosmetics?
L-Serine is a non-essential amino acid and a component of the natural moisturizing factor (NMF) of the stratum corneum.
Is Serine comedogenic?
On the Fulton scale 0/5 – non-comedogenic. For acne-prone skin, a rating of 3 or higher suggests choosing an alternative.
What's the INCI name for Serine?
The INCI name is Serine. It may also appear as: L-Serine.
See Serine in a product composition right on the store page
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