LEUCINE is graded A (Safe) by Expert·ING, based on COSING, FDA regulatory data.

LEUCINE

Safety grade: A

Leucine is an amino acid, which is a building block of proteins found naturally in your body and in foods like meat, eggs, and beans. In cosmetics, it's used in a processed form to improve hair and skin texture.

Leucine is added to cosmetics to reduce frizz and static in hair, improve moisture retention in skin, and create a smoother, softer feel on both hair and skin surfaces.

Graded using: COSING, FDA.

Last verified: May 26, 2026