Does unintentionally swallowing nasal mucus that flows down from the nose into the mouth during fasting invalidate the fast, and must one make up for the days on which this occurred due to ignorance of the ruling?

Scholarly opinions have differed regarding the ruling on swallowing phlegm or mucus if it reaches the mouth. Some, like the Shafi'is, considered it to break the fast, while others, like the Hanafis and Malikis, were lenient and deemed it not to break the fast.

A fasting person should, as much as possible, avoid swallowing phlegm. However, if it becomes difficult to avoid and an unavoidable matter, the preponderant opinion is that it is excused and does not invalidate the fast, as it falls under the general affliction (umoom al-balwa) and occurs without the fasting person's choice. This is similar to someone afflicted with a nosebleed or continuous gum bleeding, where leniency is granted for that which is difficult to avoid.