Question: Is it permissible to use toothpaste or mouthwash while fasting?
Answer: بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ، الْـحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ، وَالصَّلَاةُ وَالسَّلَامُ عَلَى أَشْرَفِ الْأَنْبِيَاءِ وَالْمُرْسَلِينَ، نَبِيِّنَا مُحَمَّدٍ، وَعَلَى آلِهِ وَصَحْبِهِ أَجْمَعِينَ، وَمَنْ تَبِعَهُمْ بِإِحْسَانٍ إِلَى يَوْمِ الدِّينِ.
The fast is invalidated when something reaches the stomach through a known passage, such as the mouth or nose, as agreed upon by all four madhāhib. The use of flavored substances like toothpaste and mouthwash during fasting carries a risk that remnants may be swallowed.
The Ḥanafī and Shāfiʿī madhhabs generally discourage the use of toothpaste and mouthwash during the day in Ramaḍān, even if not swallowed, due to the difficulty in ensuring that no trace enters the throat.
The Mālikī and Ḥanbalī madhhabs permit it provided there is certainty or high confidence that nothing reaches the throat. However, they too advise caution due to the possibility of nullifying the fast unintentionally.
Rinsing the mouth with plain water, as done in wuḍūʾ, is permitted and does not break the fast. However, excessive rinsing or gargling is discouraged during fasting hours.
Therefore, using toothpaste or mouthwash is permissible during the fast, although it is discouraged by the majority of scholars due to the risk of invalidating the fast.
وَاللَّهُ أَعْلَمُ.