Answered by Shaykh Faraz Rabbani
If any toothpaste or saliva changed by it gets swallowed one’s fast is invalidated. It is best to avoid using toothpaste while fasting, unless one can do so without endangering one’s fast. Using toothpaste is sinful, correct? A shaykh taught us that it is makruh tahriman to “use paste or tooth powder to clean one’s teeth.”
Walaikum assalam,
If a general ruling were to be given, it would be as explained by the shaykh. However, some scholars explain that:
– If one fears anything going down one’s throat, it is prohibitively disliked (makruh tahriman);
– If one is sure that nothing will go down, it is somewhat disliked (makruh tanzihan), unless there is a genuine need or excuse (such as a job appointment!)…
Walaikum assalam
Faraz Rabbani.