Tryptophan
Essential aromatic amino acid. In cosmetics – a component of NMF (natural moisturizing factor): amino acids in the stratum corneum bind water and support hydration. In amino-acid complexes works as a humectant. No standalone activity as an active.
Evidence by route
Topical application
NMF component, surface humectant. No standalone activity when applied topically, works as part of an amino-acid system.
- CIR Cosmetic Ingredient Review safety assessment.
How to read tiers A–F
- CWeak evidence. In vitro data, open-label studies, or expert consensus
Tolerability and safety
- Irritation potential
- Low
- Allergen risk
- Low
- Pregnancy
- Safe
- Suitable for
- Normal, Dry, Combination, Oily, Sensitive
About this ingredient
Tryptophan (L-Tryptophan) is an essential aromatic amino acid. The body uses it to synthesise proteins, serotonin, melatonin, and niacin (B3). In cosmetics – a component of the natural moisturising factor (NMF) of the stratum corneum. Mechanism. Within NMF it retains moisture thanks to hygroscopic properties: the aromatic ring and amino-acid groups bind water molecules. Without pronounced standalone activity as an active – it works synergistically with other amino acids and low-molecular-weight hyaluronic acid. Where applied. Amino acid complexes in moisturising serums and creams, sensitive-skin products. In Spain – in La Roche-Posay Hyalu B5, Bioderma Hydrabio, Sesderma Hidraderm lines. Use levels in finished formulas: 0.1-0.5%. Evidence base. Functional ingredient without specific RCTs using isolated tryptophan. NMF is known to make up 15-20% of stratum corneum mass, and NMF decline in dry skin and atopy is well documented (Verdier-Sevrain 2007). Safety. CIR confirmed the safety of all cosmetic amino acids in 2017. Non-sensitising, non-comedogenic. Pregnancy and lactation – safe. Usable without restrictions.
Frequently asked questions
Is Tryptophan safe during pregnancy?
Tryptophan is considered safe during pregnancy at typical cosmetic concentrations. Systemic absorption through the skin is minimal.
What skin types is Tryptophan for?
Tryptophan suits: normal, dry, combination, oily, sensitive.
What is Tryptophan and what does it do in cosmetics?
Essential aromatic amino acid.
What's the INCI name for Tryptophan?
The INCI name is Tryptophan. It may also appear as: L-Tryptophan.
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