Does swallowing blood accumulated in the mouth during sleep due to gum bleeding invalidate the fast, especially if it is difficult to ascertain whether it was swallowed intentionally or not?

Blood is impure according to the majority of scholars, and it is forbidden to intentionally swallow it. Therefore, it must be spit out if found in the mouth, and tissues can be used for this purpose. As for what enters the throat or stomach unintentionally or during sleep, there is no sin in it. However, one should not leave blood in the mouth and sleep, as there is a strong possibility of swallowing it.