A sulfur-containing amino acid. It supports hydration and joins a recovery complex. Well tolerated.
Topical application
BLimited evidence. One RCT or several controlled studies with limitations.
An amino acid that supports hydration. Safe.
Cystine is an amino acid of two joined cysteine molecules, rich in sulfur. INCI: Cystine. In a formula it works as a conditioning agent: it is part of skin and hair keratin, supports the protein structure of the stratum corneum, and helps keep softness. It appears more often in hair products and strengthening care. Its standalone cosmetic activity is mild; it is a supporting component rather than a lead active with a marked clinical effect. Pregnancy safety. Topical use, low systemic absorption, no evidence of harm. It can be used during pregnancy and lactation. Tolerance. Irritation and allergen potential are low, suitable for sensitive skin.
Irritation potential
LowAllergen risk
LowPregnancy
SafeSuitable for
The Evigrade extension adds an evidence panel to iHerb, Sephora, Druni and 12 more stores. This ingredient and every other one in the product show evidence-tier, allergen risk and pregnancy/lactation flags at a glance.
Cystine is considered safe during pregnancy at typical cosmetic concentrations. Systemic absorption through the skin is minimal.
Cystine suits: normal, dry, combination, oily, sensitive.
A sulfur-containing amino acid.
The INCI name is Cystine. It may also appear as: Цистин.
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