This is something I struggle about. Thirty years ago when I was first hired to work at a fabric store the manager held out her hands and warned me. Back then there was formeldahyde in fabrics. Her hands were covered with tiny scares due to an allergy to the formeldahyde. So I always prewashed fabrics. When I started quilting again in last few years I took classes and most of my teachers said "Don't prewash fabrics". One claimed they put a sunblock on them so they dont fade. Great, but again that is some sort of chemical, plus what else do they treat new fabric with??? So I have just started prewashing my fabrics again. Plus I wash all new quilts except for wallhangings. Those I figure aren't being wrapped around people so no need to wash after finished. So I guess my answer is yes. And I always use dye free, scent free products. I am extremely allergic to dyes and scents and have a hard time even attending quilt classes, etc due to the loads of perfumes people wear, scents from their laundry detergents, etc. Plus the scented spray starch used in one class made me ill for days, I had to leave that class early. I didn't tell people why, but if I get so ill from scents, other people are getting ill too. Scents often trigger very bad migranes for me too. Before you add a great scent to a quilted gift think of all the people who might be at the occasion where your gift might be openned.
So yes I wash them when done and think I will start washing wallhangings when done too.
Sorry if I offended anyone.
Kat