Does fasting become invalid if there is a trace of washed blood on underwear that was worn while fasting, or if one feels the taste of shampoo in the throat while bathing?

Fasting is not invalidated by wearing the aforementioned clothes, and your doubt about something reaching your throat is not considered, for the original state is the validity of your fast. And if something reaches your throat unintentionally, your fast is not invalidated by that. We warn you against obsessive whispering (waswasah) and urge you to seek knowledge.