Is it permissible to pray in undergarments from which blood and pus are discharged due to an abscess, or must they be changed before each prayer?

Scholars have differed regarding the impurity of pus. The opinion that it is pure is strong and was chosen by Ibn Taymiyyah, and it can be adopted to avoid hardship, though it is more cautious to purify it. As for blood, it is impure, but a small amount of it is excused. If clothing is soiled with an impurity that is not excused, it is obligatory to wash it without changing the clothes. If it is a small amount of an excused impurity, then nothing is required. Placing cotton on a wound to prevent the spread of impurity is good, provided it does no harm.