A method of protecting animal tissue particularly skin, from damage caused by radiation exposure, by contacting the tissue with a ketone ester, a method of protecting skin, reducing the deterioration of skin or maintaining or improving the properties of skin by applying topically to the skin a ketone body comprising (R)-3-hydroxybutyrate moieties is disclosed. A ketone body comprising (R)-3-hydroxybutyrate moieties, especially enantiomerically enriched R-1,3-hydroxybutyl-(R)-3-hydroxybutyrate, for such uses is also provided.