Is it permissible for a sick pilgrim (muhrim) or a child to wear diapers if there is a need for it, and is that considered among the prohibitions of ihram?

The well-known diapers are attached to the forbidden undergarment for a pilgrim in ihram, because they are tailored to the body. If a pilgrim in ihram needs to wear them out of necessity, there is no harm, but he must offer the fidyah (expiation) for harm, which is: sacrificing a sheep, or feeding six poor people (half a saa' for each poor person), or fasting for three days, by analogy with the hadith of Ka'b ibn Ujrah.