The dyes used to give diapers a fashionable flair may also give some babies and toddlers an allergic skin reaction, according to a new report.

In the September issue of the journal Pediatrics, they describe the cases of five children whose colorful diapers and training pants caused their skin to become red, itchy and inflamed. The babies and toddlers, who ranged in age from 9 months to 3 years, were all diagnosed with allergic Contact dermatitis - a reaction that arises when the skin comes in contact with an allergy-provoking substance, which in these cases appeared to be fabric dye.

All of the children improved after their parents switched to dye-free diapers.

Diaper rash is a common affliction of diaper wearers, but diaper dyes are a little recognized source of skin irritation, according to Dr. Karen Wiss of the University of Massachusetts Medical School in Worcester.

For parents, location is the best “best clue” to whether their baby’s diaper rash is an allergic reaction to dye, Wiss told. If the skin irritation lines up with colored areas of the child’s diaper, the dye may be to blame.

In one of the cases Wiss and her colleagues describe, a 2-year-old boy developed hives underneath the blue-dyed waistband of his diaper. In another, a 9-month-old had a “well-demarcated” rash that matched up with the green-colored areas of his diaper.

Two of the children underwent skin testing that confirmed they had allergies to so-called disperse dyes. These dyes, which are used to color synthetic fibers like polyester, may release from fabrics in the presence of friction and sweating, Wiss and her colleagues note.

Still, though these cases call attention to the potential for diaper-dye reactions, Wiss said that the “vast majority” of babies and toddlers can probably wear colorful diapers without a problem.

SOURCE: Pediatrics, September 2005.