His statement, “if it reaches his mouth,” refers to the point at which one can discern the taste of food. If the phlegm does not reach the mouth—for example, if he feels it descend from his head and go into his stomach—it does not invalidate the fast, because it has not reached the exterior of the body. The mouth is regarded as part of the exterior. Thus, if it reaches the mouth and he then swallows it, his fast is invalidated. But if it does not reach the mouth, it remains classified as internal and does not invalidate the fast.
There is another view in the school of law: that it does not invalidate the fast even if it reaches the mouth and he swallows it. This view is more preponderant, because it has not left the mouth, and swallowing it is not considered eating or drinking. Therefore, if he swallows it after it has reached his mouth, it does not invalidate his fast. However, before he does this, we say: Do not do it; avoid this matter, since the issue is as described. Phlegm is not like swallowing saliva; rather, it is a substance whose presence in the mouth is unusual. Saliva, by contrast, is different. The disagreement over whether phlegm invalidates the fast is stronger than the disagreement over whether all saliva invalidates it, and the matter is clear. Yet, as we said earlier, swallowing phlegm is forbidden because of its repulsiveness and the harm it may cause.
Question: If blood appears from his tongue, gums, or teeth, is it permissible for him to swallow it?
Answer: It is not permissible, whether for one who is fasting or otherwise, due to the generality of Allah’s statement: “Forbidden to you are carrion and blood” [al-Ma'idah 5:3]. If this occurs to a fasting person, it invalidates his fast. Therefore, a person must take care not to swallow blood that comes from a molar after it is extracted during the fast, or after it was extracted at night and blood continues to flow from it, for this blood invalidates his fast and is also forbidden.
“It is disliked to taste food without a need, or to chew strong gum. If he finds the taste of either in his throat, his fast is invalidated, …”
His statement, “It is disliked to taste food without a need,” means that it is disliked for a person to taste