Odor coming when running water

Hi,
I smell odor when I run cold or hot water on 2nd floor sink (smells like medicine).
There is no odor from 1st Fl. sinks. The odor comes from the faucet (not from the drain - same odor when I run water into a pot).

Suggestions I found on the web don't seem to apply here: It can't come from hot water tank because it affects cold water too, and it can't be caused by dead end pipes since it began at the same time with cold and hot water.
I tried closing water supply and draining cold water from the system - it did not help.
My plumber mentioned the issue could be related to anaerobic pipe in old houses, which is located near the highest sink, but it is buried, so there is no much I can do about it without breaking the wall.

Any suggestions?

 

I'm not the pro in this forum.

I've never heard of anaerobic pipe. I've heard of metal or galvanized pipe which uses an anaerobic paste to seal the threads. So in your case it could be hard to tell if the smell is just from the galvanized pipe or the compound used to seal the threads.