Answered by Shaykh Amjad Rasheed
Is it permitted for a man to change his baby’s diapers?
Yes, it is permitted for a man to change his small child’s diaper, and also the diapers of another’s child.
In such a case, it would also be permitted for him to look at the private parts of the child, whether male or female, because of the need to clean and apply medicine [when the need arises]. This has been explicitly stated by Allama al-Shabramallisi in Hashiyat al-Nihaya.
It should be noted, however, that touching the private parts with one’s inner palm without a barrier invalidates ritual ablutions (wudu) in the Shafi`i school, even when the one touched is small.