Can I brush my teeth or use a miswak while fasting?

Why the scholars permit it

The ruling rests on a simple principle: the fast is broken by something reaching the body's interior, not by contact with the mouth. Cleaning the teeth — with a stick, a brush, soap or paste — does not itself break the fast. What breaks it is deliberately swallowing what should have been spat out.

Shaykh Ibn Baz was asked directly whether toothpaste breaks the fast and answered that it does not, nor does the miswak, nor cleaning the mouth with soap or anything else. He added the condition that governs everything:

"Toothpaste does not break the fast of the one who is fasting, and likewise the miswak, and likewise cleaning the mouth with soap or something else — all of this does not break the fast of the one who is fasting. But a person must beware of anything entering his interior."— Shaykh Ibn Baz, Majmu' al-Fatawa

IslamWeb (fatwa 40013) gives the same ruling in the same terms: permissible, on condition that nothing is swallowed.

The miswak has its own evidence

The miswak is not merely tolerated during a fast — it is a sunnah the Prophet ﷺ encouraged, and Shaykh Ibn Baz held it is recommended at the beginning of the day and at its end. Some scholars disliked using it after midday, reasoning that the change in the fasting person's breath is something beloved to Allah and should be preserved. Ibn Baz judged that view weak, and gave his evidence:

"Were it not that I would burden my ummah, I would have commanded them to use the miswak at every prayer."— Sahih al-Bukhari and Sahih Muslim 252, from Abu Hurayrah

Since the command would cover the Dhuhr and Asr prayers, both of which fall after midday, the miswak cannot be disliked at that time. The Hanbali manual Sharh Muntaha al-Iradat records the same disagreement within the school — the relied-upon position being that it is disliked after midday, with a reported view that it is merely permitted, and another that it remains recommended.

What actually breaks the fast

The line the scholars draw is between contact and swallowing.

• Deliberate swallowing breaks the fast: if you intentionally swallow paste, mouthwash or the taste of paste remaining in your mouth, the fast is invalid. IslamWeb notes that the lingering taste is itself evidence that particles of the paste remain.
• Accidental swallowing does not: if something reaches your throat without intent, or overpowers you, or you forget, your fast stands and no make-up is due. Ibn Baz states this explicitly.
• Spit thoroughly: Ibn Baz's repeated instruction is to be careful and to make every effort to spit out what is in the mouth so that nothing is swallowed.

Why they still advise delaying it

Both scholars permit the paste but prefer you avoid it during the day — not because it is unlawful, but because it is hard to control. Ibn Uthaymeen explains the reasoning: toothpaste has a strong penetration and can reach the throat and stomach without the person sensing it, and there is no necessity driving you to use it in daylight. His advice is to move it to the night, since the night is wide enough.

He grounds this in the Prophet's ﷺ instruction to Laqit ibn Sabirah:

"Exaggerate in rinsing the nose, unless you are fasting."— Sunan Abu Dawud 2366, from Laqit ibn Sabirah

The exception is given precisely so that water does not slip down unawares — the same reasoning applies to a substance as penetrating as paste.

In practice

• Miswak: use it freely at any hour of the day. The dislike of using it after midday is a weak position.
• Brush and paste: permitted, but brush carefully, spit thoroughly, and rinse. If you can, move it to after iftar — that is the safer course both scholars recommend.
• If you taste paste afterwards: avoid deliberately swallowing your saliva while the taste remains.
• If you slip: nothing is owed for an accident; only deliberate swallowing invalidates the fast.

Key takeaways

• Using a miswak while fasting is permitted at any time of day, and the view that it is disliked after midday is weak.
• Toothpaste does not break the fast so long as none of it is swallowed.
• Deliberately swallowing paste, or the saliva carrying its taste, invalidates the fast.
• Accidental swallowing — without intent, by being overpowered, or in forgetfulness — does not invalidate the fast and requires no make-up.
• Ibn Baz and Ibn Uthaymeen both advise delaying toothpaste until after iftar, because of how easily it reaches the throat unnoticed.

Further reading

• Majmu' al-Fatawa wa Maqalat — Shaykh Ibn Baz
• Fatawa Nur 'ala al-Darb — Shaykh Ibn Uthaymeen
• al-Majmu' — Imam al-Nawawi

And Allah knows best.