You have a water leak ether from the roof, and attic or from the apartment above you or, do you habe an upstairs bathroom over that area?

sometimes animals live up their too it could be urine

you need to explore ldoes the ceiking feelwet?

it should i can see it

It's a pretty good leak. I'd get on that fast because when drywall is involved repair gets very pricey. We had to do it sev yrs ago when we had a roof leak.

Check your home for fungus/mold growth. In my case, the cause was an overgrowth of fungus in an old tub of whey protein at the back of a cupboard. The spores were irritaing and causing the sensations on the skin. Upon removal of the tub, the problem resolved practically overnight.