Fundamental constituents of all proteins found in the body, such as: alanine, arginine, asparagine, aspartic acid, cysteine, cystine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. Some of these amino acids can be synthesized by the body; others (known as essential amino acids) must be obtained from protein in the diet.
In skincare 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 aging. 
References for this information:
European Surgical Research, January-April 2002, issues 1-2, pages 53-60
About the Experts
Paula Begoun is the best-selling author of 20 books about skincare and makeup. She is known worldwide as The Cosmetics Cop and creator of Paula’s Choice Skincare. Paula’s expertise has led to hundreds of appearances on national and international radio, print, and television including:
The Paula's Choice Research Team is dedicated to busting beauty myths and providing expert advice that solves your skincare frustrations so you can have the best skin of your life!