Many bubble-bath formulas contain perfumes and dyes, as well as sodium laureth sulfate (the stuff that creates the bubbling action). Prolonged exposure to these ingredients  -- such as sitting in the tub for 40 minutes or more  -- can break down the skin's natural barrier to infection, causing redness and swelling in both boys and girls. When the skin in and around the vaginal area is affected, the irritation can mimic the symptoms of a urinary tract infection (UTI), such as burning during urination, or even lead to a UTI by allowing bacteria easy access to the urinary tract. At the first sign of skin irritation, parents should discontinue bubble baths until the skin clears.

Sensitivities to harsh ingredients lessen considerably after adolescence, when the skin toughens enough to resist such reactions. Until then, look for bubble baths without perfumes and dyes and with little or no sodium laureth sulfate (it shouldn't be one of the first three ingredients). To minimize irritation to your child's skin, limit bubble baths to once a week.