Provided is use of a peptide, or a derivative of a peptide, in the manufacture of a medicament effective in alleviating or preventing periodontal disease, wherein the peptide comprises an amino acid sequence present in an .alpha.-S2 casein precursor, said sequence comprising 3 or more amino acids, and not comprising at its N-terminus the N-terminal amino acids of the full .alpha.-S2 casein precursor. The peptide may alternatively be any peptide having an .alpha.-S2 casein fragment activity. Further provided is use of a peptide, or a derivative of a peptide, in the manufacture of a medicament effective in alleviating or preventing an effect of aging in skin, wherein the peptide comprises an amino acid sequence present in a n .alpha.-S2 casein precursor, said sequence comprising 3 or more amino acids, and not comprising at its N-terminus the N-terminal amino acid of the full .alpha.-S2 casein precursor. The peptide may alternatively be any peptide having an .alpha.-S2 casein fragment activity.