Have you ever gone shopping when the new clothes come into the stores, and your eyes hurt and you get a headache? The reason, most people think, is the dye. Not so...it's the formaldehyde. And if the clothes/material is coming from China, it is even worse.
I don't have a huge stash (yet,lol) but over the years have learned to wash my fabrics, especially all the muslin, because I buy it to use in cooking and baking. And if you are sensitive, NEVER wear "the new" off of clothes. Wash them first.
I have worked at both the lower end of the retail stores and the upper end of high $$$$ clothing stores, and when the new lines come in, the chemical smells would make your eyes cross.