بسم الله الرحمن الرحيم
When there is a wound on the body of a person, doctors sometimes place a bandage over the wound to aid in healing. If removing this bandage and doing masah over the actual wound is harmful, then it will be necessary to do masah on majority of the bandage. If the condition is so severe that even doing masah on the bandage is harmful, then out of necessity, it will be permissible to leave out the masah as well.
أفضل التطبيق العصري على مسائل القدوري
للمفتي محمد أشرف الاشاعتي
Vol.1 Pg.193