Amino acid composition for use in the treatment of mucositis in patients suffering from head and neck cancer, undergoing radiation therapy and/or chemotherapy, the composition comprising an active agent, said active agent comprising the amino acids: glutamine, leucine, isoleucine, valine, lysine, threonine, histidine, phenylalanine, methionine, tryptophan, tyrosine, and cystine, wherein the glutamine:leucine weight ratio is comprised in the range 4.3 to 5.3.