Is it obligatory to wash the hand if it touches something in the kitchen, due to the possibility of it being defiled by menstrual blood?

The basic principle regarding items found in the kitchen and elsewhere is ritual purity (ṭahārah). Leave off these whisperings (waswas) and do not give in to such delusions, for giving in to whisperings leads to great evil. It is sufficient for you to act upon the fundamental principle, which is purity, and build upon it. Therefore, do not judge something to be impure unless you have absolute certainty regarding that.