Humectant

Citrulline

An unusual amino acid that is not part of the standard set of 20 — it is not included in proteins but plays a key role in the urea cycle and the synthesis of nitric oxide (NO). In cosmetics, it moisturizes, supports microcirculation, and protects against osmotic stress.

Unusual amino acidPrecursor of NOOsmoprotectantMoisturization

✓ Safe

Comedogenic Rating

0/5

Irritation Potential

0/5

What is it?

L-Citrulline (INCI: Citrulline) — a free amino acid, not included in proteins. Molecular weight ~175 Da. Well soluble in water. In the body: an intermediate metabolite in the urea cycle (ornithine → citrulline → arginine). Precursor of arginine → precursor of NO (nitric oxide). NO: vasodilation → improved microcirculation. In plants (watermelon, melon, cucumber): osmoprotectant under drought → adaptive molecule. In the skin: NMF component (small amount), osmolyte protection of cells. Functions in cosmetics: moisturizer, support for microcirculation, osmoprotectant.

Moisturizers with "urban energy" or "oxygen boost" positioning, products for dull and tired skin, watermelon or "vegetal amino acid" formulas.

Key Benefits

✦

Moisturization and osmoprotection of cells

Citrulline — a hygroscopic amino acid that attracts water. As an osmolyte in plant cells (watermelon survives in drought conditions due to the accumulation of citrulline): protects cells from osmotic stress. When applied to the skin: moisturizes the stratum corneum and protects keratinocytes from dehydration stress (dry air, air conditioning, wind). Effective in combination with taurine and sodium PCA.

◈

Precursor of arginine and nitric oxide

Citrulline → (converts) → Arginine → Nitric Oxide (NO). NO: causes vasodilation of skin capillaries → improved microcirculation → more oxygen and nutrients for cells. Result: products with citrulline can enhance the "freshness" and radiance of the skin by boosting microvascularity. Also, NO has a weak antimicrobial effect.

✧

Energy support for cells — urea cycle

Citrulline participates in the detoxification of ammonia through the urea cycle. Accumulation of ammonia (a byproduct of amino acid breakdown) is one of the factors of cellular stress and aging. Citrulline supports normal ammonia excretion → reduces cellular stress. In combination with glutamine and arginine: supports the "metabolic health" of skin cells.

Suitable for

Dull skinDehydrated skinTired skin

Main Actions

✓ Osmotic moisturization✓ Precursor of NO for microcirculation✓ Cellular osmoprotectant

Citrulline and watermelon in cosmetics

Watermelon (Citrullus lanatus) — a natural source of citrulline. Watermelon extract in cosmetics: contains citrulline, lycopene (antioxidant), and vitamin C. Citrulline in the INCI composition: either as a free amino acid 'Citrulline' / 'L-Citrulline', or as part of 'Citrullus Lanatus (Watermelon) Fruit Extract'. Both options are beneficial, but the synthetic free form is more concentrated and predictable.

CategoryHumectants

Frequently Asked Questions

What does Citrulline do for skin?

Moisturizers with "urban energy" or "oxygen boost" positioning, products for dull and tired skin, watermelon or "vegetal amino acid" formulas.

Who should use Citrulline?

Citrulline is suitable for: Dull skin, Dehydrated skin, Tired skin.

Are there any warnings about Citrulline?

Check if this ingredient works for your skin — analyze your full product formula for free.

Analyze your product