Is it obligatory to rinse the mouth after spitting out food remnants or pieces of skin, or is it sufficient to spit them out and swallow the saliva? And do these pieces, or phlegm mixed with blood, break the fast if swallowed? And is there a difference between spitting out water after rinsing the mouth for ablution and spitting it out after rinsing for cleaning?

It is clear that the questioner has excessively indulged in obsessive thoughts. The cure for obsessive thoughts is to ignore them. One who intends to fast should not be dragged by obsessive thoughts.

Rinsing the mouth and cleaning the teeth after suhoor (pre-dawn meal) is mustahabb (recommended) not wajib (obligatory). What is obligatory is not to swallow anything that invalidates the fast.

Swallowing what is between the teeth does not invalidate the fast unless it is abundant, avoidable, and the fasting person intentionally swallows it. Cleaning the teeth with a brush and floss makes the presence of avoidable food particles almost impossible.

There is no need for all the precautions mentioned by the questioner regarding swallowing saliva or scrutinizing it for fear of it containing unseen food residues or membranes. This is blameworthy extremism (tanattu'), and it has led her to harm herself. Allah Almighty says: "And He has not placed upon you in the religion any difficulty."

Saliva mixed with blood: It is not permissible to swallow it if it is possible to spit it out. However, if it is abundant and continuous, making it difficult to avoid, then it does not invalidate the fast, according to many scholars.

There is no difference between swishing water for ritual ablution (wudu') and swishing it to clean the mouth, except that the mouth-rinsing in wudu' – according to some jurists – is achieved by any movement of water in the mouth, which may not be sufficient for cleaning.