painkillers and little pains

i’m posting this question here because i supposed some connection with religion in what i’m going to ask…

is there some prohibition or is highly adviced from religion not to take painkillers for “little” pains? (as when a woman has her period,she may feel headache,strong bellyache…or when you just have some headache,for example)
i’m asking this because all friends i talked to don’t feel like taking medicines to relieve pain (two girls were in their period and one of those seemed to have great bellyache…)
even a guy who suffered from sciatic nerv and pain in the back because of work didn’t want to take some medicine,even after 15 days working with that kind of pain.
when i suggested them to take some painkillers they all seemed not to approve the fact of taking medicines…why? is something related to islam? if so,can you tell me where it comes from?
thanks to you all!

This is a pure case of illiteracy and not Islam. Moslems were the first to practice medicine ( and still do) among many other evidence based sciences . So logically, to practice medicine requires, among many other things, the use of anesthesia medications to perform surgical procedures or other pain medication to control pain. Clear.