Question: If one's saliva becomes thick while fasting, does it break fast to swallow it? What if you cough up phlegm and swallow it? What if you have chronic mucous in your throat, does swallowing it break fast? Lastly, if mucous flows down the back of your throat persistently, do you have to constantly intercept it and spit it out, or can you swallow it?
Answer: It does not break the fast to swallow spit or phlegm as long as it was not from outside the mouth. As long as it remained in the mouth and was swallowed, it does not harm the fast. If someone had spit outside the mouth, then brought it into the mouth and swallowed it, however, it would break the fast, like any other substance from outside the mouth.