A diaper or a nappy is a type of underwear that allows the wearer to urinate or defecate without using a toilet, by absorbing or containing waste products to prevent soiling of outer clothing or the external environment. When diapers become wet or soiled, they need to be changed by the wearer or often by a second person, such as a parent or caregiver. Failure to change a diaper regularly can result in skin problems around the area covered by the diaper.