1- The cast, splint or bandage must not transcend the place that needs care and the necessary portions surrounding it.

2- It is not a condition that one should be in a state of purity before putting them on, neither is there a prescribed time limit for wiping over them. As long as there is a need for them to be worn, it is permissible to wipe over them even when removing the greater state of ritual impurity. But when the need for their use ceases, they must be removed and henceforth the parts underneath must be washed during wudu’ and bathing.

3- As for band-aids and bandages etc., which can be removed easily, the following should be observed:

a- If they are easy to remove and washing the part underneath will not cause any harm or delay healing, it should be removed and the portion underneath be washed, after which they may be replaced.

b- If they are not easy to remove and washing the injury may prolong the healing process, then they should be wiped over during https://www.al-feqh.com/en/wiping-over-socks-casts-and-bandages-for-wudu-ablution" rel="nofollow - al-wudu ’ and bathing.

source: https://www.al-feqh.com/en