I am wondering if in old tradition in Jerusalem servants were allowed to do house work when they were niddah. Thank you.

Thank you for your interesting question, which, please God, will hopefully soon return to become halachically practical. Firstly, these issues apply to all niddah and post-childbirth women without regard to their working status (whether servants or bosses). Regarding regular food (chulin or “secular”), there’s no problem for anyone (even a kohen) to touch or eat food which has become tameh (“spiritually impure”), and it’s not difficult for a kohen to purify himself afterwards, enabling him to eat holy food in purity. Aside from the laws of marital relations (which are practiced today, as well), the intricate laws of spiritual purity during the niddah (menstrual) period, just limit those women regarding jobs that necessitate working with food that needs to be tithed (= if trumot have yet to be taken, it’s a problem). Nevertheless, there was a significant difference between the homes of kohanim (priests) where much of the food and vessels were kodesh (=holy, like truma and trumat ma’aser which they were given by others) and need to remain tahor (“spiritually pure”), as opposed to the homes of most of Israel, where after the tithing, all of the food is chulin (=“secular”) and could be touched by anyone. Among other factors that would need to be taken into account to enable the tithing in tahara (“spiritually purity”) would be that furniture should be attached (e.g. with screws) to the ground, and that way they don’t become tameh (“spiritually impure”) from niddot sitting upon them. In addition, clay vessels were relatively inexpensive and were close to being considered “disposable” (today, disposable dishes would clearly make things easier, and most poskim hold that plastic dishes don’t receive tum’ah, so they could be used, as well). An additional difference in modern cities is that most homes buy their fruits and vegetables in supermarkets or groceries and need not tithe anything themselves. Nevertheless, before going up to Jerusalem for Pesach or festivals, all men and women would have to purify themselves anyway. These would be some of the practical ramifications. With prayer that the dealing with these now theoretical issues will merit their speedy return to being practical, Rav Ari Shvat