He was asked:
About a person who has sores on some of the body parts washed during ablution. Pus seeps from these sores and spreads beyond them over the area that must be washed. He cannot remove it from that area without also removing it from the sores, which causes him hardship. Physicians do not consider its removal harmful to him, but he experiences pain and hardship from removing it repeatedly when performing ablution. Must he remove it so that water reaches the covered portions of the area that must be washed, even if this causes him hardship, given his strong expectation concerning what follows those sores—or is he not obliged to do so?
He answered:
Praise be to Allah. If removing it would worsen the illness or delay healing, he is not obliged to remove it.
If it would do neither, he must remove it—unless it is a small amount comparable to the discharge that collects around the eye or something similar. He is not obliged to remove that. And Allah knows best.