Question: Toothpaste contains some sugar ingredients which a person tastes while using it, keeping in mind that the normal taste of food takes place by the dissolution of the food within the saliva, and then its penetration to the taste receptors. Accordingly, if the tasted matter dissolves within the saliva then, most probably, no one can avoid swallowing it.
A- Is it permissible for a fasting person to use toothpaste, keeping in mind that they can use the toothbrush only?
B- What is the ruling on using mouthwash?
C- It was reported through a good chain of transmission from Ibn ‘Abbass (Al-Irwaa’, p. 937) that he (may Allaah be pleased with him) did not see any harm in tasting honey, butter, and similar foods and then spitting it out while one is observing Sawm (Fast). This view was also reported from some Salaf (righteous predecessors). Thus, after knowing the way in which food is tasted, what is the ruling on tasting food by a fasting person
Answer: There is no harm in using toothpaste during Sawm; however, one should spit out what has been dissolved of the toothpaste in the mouth; and if something from it goes unintentionally into the throat, it will not affect Sawm... read more here.