It was narrated on the authority of Abu Hurayrah, may Allah be pleased with him, that the Prophet said: "Had it not been for the fact that I would put my Ummah (nation) to trouble, I would have commanded them to use the Siwaak (teeth-cleansing stick) before every prayer." [Al-Bukhari and Muslim]
It was narrated on the authority of ‘Aa’ishah, may Allah be pleased with her, that the Messenger of Allah said: "(Using) the Siwaak purifies the mouth and pleases the Lord." [An-Nasaa’i] [Ibn Khuzaymah: Saheeh (Authentic)]
Ibn ‘Umar, may Allah be pleased with him, said, "One (the fasting person) could brush his teeth with the Siwaak at the beginning as well as at the end of the day.”
It was further narrated that he said, “There is no harm for the fasting person to brush his teeth with the Siwaak, be it wet or dry.”
It was narrated on the authority of Mu‘aath, may Allah be pleased with him, that he said, “The Messenger of Allah commanded them (i.e., people) to use the Siwaak although he knew for certain that the unpleasant smell would remain in the mouth of the fasting person even after brushing his teeth with the Siwaak. He would not have commanded them to leave their mouths with that foul smelling on purpose, for there is nothing good in that, except the one who cannot use it (the Siwaak) for an excuse, he can do so (i.e., not use the Siwaak).”
It was narrated on the authority of Anas ibn Maalik, may Allah be pleased with him, that he would apply kohl while fasting.
It was narrated on the authority of Al-Hasan that he saw no harm in applying kohl while fasting.
It was narrated on the authority of Az-Zuhri that he said, "For the fasting person, there is no harm in applying kohl.”
Benefits and rulings
First: The virtue of the Siwaak, which is confirmed to the extent that the Prophet very nearly enjoined it upon Muslims at the time of every obligatory prayer.
Second: The compassion of the Prophet for his Ummah and his removing of hardship from them.
Third: It is permissible for the fasting person to brush his teeth with the Siwaak at the beginning as well as at the end of the day; and there is no difference between the fasting and non-fasting people in terms of its (i.e. using the Siwaak) being an act of Sunnah, because the Hadeeths narrated about it are general.
Fourth: For the fasting person, there is no difference between the wet and dry Siwaak (in terms of permissibility).
Fifth: If the fasting person uses the Siwaak, and blood emerges from between his teeth or gums, there would be no harm in that and nor would his fast become invalid, provided that he does not swallow the blood.
Sixth: It is permissible for the fasting person to apply kohl and use eye or ear drops, even if he finds the taste of that in his throat, for neither the eyes nor the ears have been mentioned (in Islamic texts) and neither are they in the position of those things mentioned among the inlets of food and drink.
Seventh: If, however, the nose drops reach the stomach, it would break the fast, for the Prophet forbade the fasting person from exaggerating in snuffing water into his nostrils. However, should it not reach the stomach, there is no harm on him.
Eighth: It is permissible for the fasting person to use an asthma atomizer which reaches the lungs, as that does not break the fast.
Ninth: The medicinal injection, be muscular or in the vein, does not break fasting, even if its taste is detected in the throat. This is unlike the nutritious injection, which makes one free of need for food and drink, and this, of course, breaks fasting.
Tenth: If the fasting person needs a nutritious injection or anything like it which would break fasting, then he should break fasting for his ailment and afterwards make up for the missed days of fasting.
Eleventh: If the fasting person uses a strong-smelling ointment, the taste of which is detected in his throat, he would not break his fasting by this, for any smell or scent, no matter how strong it might be, does not break fasting.
Twelfth: Suppositories that are given to the patient do not break fasting, which means that it is permissible for the fasting person to use them.
Thirteenth: Toothpaste, like Siwaak, does not break the fast. However, one should be careful not to let it reach the stomach. If something thereof reaches the stomach unintentionally, nothing would be due on him, and if he were to delay using the toothpaste till night, it would be more prudent.
Fourteenth: Gargling medicine does not break fast as long as the fasting person does not swallow it. However, the fasting person should delay this until the night unless there is a dire need for using it during the day.
Fifteenth: There is no harm in using an atomizer to remove the bad smell of the mouth, provided that its substance does not reach the throat.
Sixteenth: There is no harm in swallowing one's saliva, and there is no dispute in that matter. However, it is impermissible to swallow sputum and mucus as that is something avoidable.
Seventeenth: There is no harm in using the clyster (enema) and this does not break the fast.