Diaper dermatitis is a common problem in outpatient pediatric office settings. Although most diaper rashes represent a form of contact dermatitis in response to irritants in the diaper environment, other rashes may be the result of an allergen in the diaper. On the basis of clinical examination results for 5 patients and patch testing results for 2 patients, we suspect that the patients demonstrated allergic contact dermatitis in response to the various blue, pink, and green dyes in diapers. Although topically administered corticosteroids are useful in the treatment regimen, the preferred treatment for allergic contact dermatitis in the diaper area is the use of dye-free diapers for allergen avoidance. Patch testing may also be valuable in identifying the allergen, because allergen avoidance is the key to prevention of recurrent disease.