Lactic acid versus salicylic acid for keratosis pilaris

People with keratosis pilaris — the rough, bumpy skin often seen on the upper arms and thighs — were randomly assigned to apply either 10% lactic acid cream or 5% salicylic acid cream twice daily for three months, then followed for four more weeks. Bumps fell by an average of 66% with lactic acid and 52% with salicylic acid. Skin hydration rose in both groups and stayed up through the follow-up period. Side effects were limited to mild local irritation. The important limitation is that there was no placebo group, so this shows lactic acid works better than salicylic acid here, but it cannot tell you how much of the benefit came from the acid rather than from moisturising the skin twice a day for twelve weeks.