When exactly can you play cards like Cure spell? Can you use it on someone else's turn or only on your turn? Could you use detect magic on someone else's turn?
In other recent threads, Vic has suggested a good guideline that you can play a card unless it specifically says you can't.
Remember that 'you' refers to the person playing the card though. So if you played detect magic on someone else's turn, you'd be examining the top card of your own location (and potentially acquiring the blessing or boon with a magic trait).
You can use Cure on someone else's turn, but not in the middle of a check.
It is one of the nice things about being in the same location as a healer.