What is the best treatment for diaper rash?

What the evidence says

Most diaper rash is simple irritation from urine and stool sitting on the skin too long. The Canadian Paediatric Society recommends changing diapers often, cleaning gently with mild soap and water or unscented wipes, patting dry, and giving some diaper-free air time before applying a barrier cream such as petroleum jelly or a zinc oxide paste. A recent systematic review of barrier creams found that zinc oxide paste and clotrimazole (an antifungal) both reduced diaper dermatitis compared to no treatment, and that zinc oxide performed as well as or better than plain petroleum jelly in some trials.

One randomized trial also found zinc oxide cream worked better than talcum powder for prevention. If the rash is bright red with sharp, well-defined edges, worse in the skin folds, or has small satellite bumps, it may be a yeast (candida) infection, which the Canadian Paediatric Society says needs a doctor-prescribed antifungal cream rather than just a barrier cream. American paediatric guidance similarly notes that irritant rash usually spares the skin creases while candida involves them, and suggests adding antifungal treatment if a rash lasts more than about 3 days or follows antibiotics.

See a doctor if the rash doesn't improve within a few days of home care, looks infected (yellow crusting, weeping, pimples, spreading redness), is very painful, or occurs in a baby under 3 months old. Over-the-counter antibiotic ointments are not recommended for routine diaper rash since some ingredients can worsen irritation.