Answer
Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Scholars have different opinions on whether or not swallowing mucus invalidates the fast. However, the view that says that it doesn’t break the fast seems to be the most correct.
Responding to your question, Dr. Wael Shihab, PhD in Islamic Studies from Al-Azhar University. He is currently the Imam of the Downtown Toronto Masjid in Canada states:
In fact, scholars have different views on whether or not swallowing mucus breaks the fast. But, the opinion that says it doesn’t break the fast seems to be the most correct.
In this context, Sheikh Ibn Uthaymin says,
Phlegm and mucus that do not reach the mouth do not break the fast. This is the only opinion expressed on the matter in the (Hanbali) school of law.
If the phlegm and mucous reach the mouth and then the person swallows it back down, there is disagreement among the scholars regarding whether it breaks the fast or not:
One opinion is that it does break the fast. Scholars who hold this view compare swallowing phlegm and mucus to eating and drinking.
The other opinion is that it does not break the fast. Scholars who hold this view regard phlegm and mucus to be comparable to saliva. Even if a person gathers saliva in his mouth and swallows it, this will not break his fast.
In a case where the scholars are divided in their opinions, then the matter must be referred back to the Quran and Sunnah. Since we are in doubt about whether swallowing phlegm and mucus invalidates the fast, we must consider that the default assumption in Islamic Law in the absence of other evidence is that it does not do so.
Based on this default assumption, we would say that swallowing phlegm and mucus does not break the fast.
Allah Almighty knows best.
Editor’s note: This fatwa is from Ask the Scholar’s archive and was originally published at an earlier date.