A tetrapeptide having antioxidant activity is provided. The tetrapeptide has a structure comprising, in amino acid sequence from N-terminus to C-terminus: tryptophan-X-tyrosine-X; wherein X is arginine, lysine, histidine or any positively-charged amino acid derivative such as 5-hydroxylysine, ornithine, 2,4-diamino-butyrate and 2,3-diamino-propionate. Each amino acid of the sequence or its Homo-amino acid derivative is independently of the D configuration (D-stereoisomer) or of the L configuration (L-stereoisomer), and the C-terminal comprises one selected from the group consisting of carboxyl (—COOH), and carboxamide (—CONH2). A composition stabilized to oxidation or having antioxidant activity and a method for attenuating effects of free radicals on a keratinous material are also provided.