If stains remain, use slightly warm water, soak the menstrual blood side down in a detergent solution, and then wash.
(However, please note that using hot water over 45℃ may cause blood to coagulate.)
Oxygen bleach does not lift dirt and remove it like detergents do, but rather breaks down the dirt, making it easier for the fibers to break down along with the dirt.
Therefore, we do not recommend using it on cloth napkins. 
