Methionine Good Antioxidant Anti-Ageing Hydration Methionine description Methionine is a type of amino acid, which are fundamental constituents of all proteins found in the body. Some of amino acids can be synthesised by the body; others (known as essential amino acids) must be obtained from protein in the diet. In skin care products, amino acids act as water-binding agents, and some have antioxidant properties. Amino acids can be combined with other ingredients that have skin-restorative ability to work in unison to fight signs of ageing. [br] [br] Note: Research has shown amino acids for skin work best when several of them are combined. For this reason, we rate the amino acids as a group more highly than some individual amino acids. Although some individual amino acids have distinctive benefits compared to others, you would be selling your skin short if you only focused on one particular amino acid.