Provided are an AGE breakdown agent and an agent for preventing, inhibiting, or ameliorating skin deterioration stemming from AGE buildup, said agents containing, as an active ingredient, either: (i) an unsaturated fatty acid and / or a pharmaceutically-permitted salt, ester, amide, and / or glyceride thereof; or (ii) a vegetable oil (evening primrose oil, pequi oil, meadowfoam oil, shea oil, etc.) that contains an unsaturated fatty acid and / or a glyceride thereof. An agent which contains either (i) or (ii), in addition to lactic acid, glycolic acid, salicylic acid, malic acid, citric acid, phytic acid, and / or a pharmaceutically-permitted salt of one or more of said acids, is a more effective agent for preventing, inhibiting, or ameliorating skin deterioration stemming from AGE buildup.