Lysine

Lysine is an essential amino acid, meaning your body can’t make it on its own and must get it from diet or topical sources. In skincare and haircare, it’s usually used as a supporting ingredient rather than a headline active. Because amino acids are natural building blocks of proteins, lysine can help formulas feel more skin-friendly and may support the look of healthy, resilient skin and hair.

For skin, lysine is often included in products aimed at hydration, barrier support, or overall conditioning. It can help attract and hold moisture as part of a blend with other amino acids and humectants, which may make skin feel softer and less tight. In hair products, it may contribute to a smoother, more conditioned feel and support the appearance of stronger strands. People with dry, stressed, or barrier-compromised skin may especially appreciate formulas that include it.

Caveat: lysine is not a dramatic spot treatment or anti-aging powerhouse on its own, and its benefits are usually subtle. It works best as part of a well-designed formula, alongside ingredients like glycerin, ceramides, or peptides. As with any ingredient, very sensitive users should check the full formula, since irritation is more likely to come from the product overall than from lysine itself.