What is the ruling on fasting after feeling something in the mouth and swallowing saliva with doubt about the presence of food?

If you unintentionally swallow a hair or food residue, your fast is not invalidated, according to the soundest opinions of scholars. Doubting whether you swallowed it does not affect the validity of the fast, as the default is that the fast is valid. There is no need for excessive strictness in wiping away traces of saliva. We advise you not to give in to such doubts and feelings to avoid falling into waswas (obsessive whispering).