I do prewash all my fabrics. 1. To remove all the chemicals used for finishing the fabric. 2. Preshrink it. Fabrics will shrink at different rates than others even if they are from the same manufacturer.
My main reason is to remove all the chemicals. I have developed a "formaldhyde intolerance". This is one of the main chemicals in fabric finishing.
I had noticed that sometimes my hands and arms would itch when handling fabric. I just thought it was from the lint and didn't think much of it. One day I woke up and noticed my eyelids were very red and swollen and itched like mad! Again, didn't think much of that except maybe allergies were acting up a bit. I was working on a king sized quilt for a wedding gift and really needed to get it done. So I kept plugging away. In the mean time, I kept scratching my hands and arms and rubbing my eyes to somewhat "soothe" the itch. After rubbing my eyes, sometimes I would find an eyelash or two, hmm no biggie, keep going.
After two weeks, the quilt was FINISHED! YAHOO, in plenty of time for the wedding. All this time, I still had the red angry swollen eyelids. One day I took a very close look at my eyelids. Almost ALL of my eyelashes were gone! What eyelashes remained were misshapen and going in all different directions. Okay, time to call the doc.
He took a strong look at my skin and my eyes. Then he went and got a dermotologist and opthomalogist and brought them into the room. By now I was feeling like a specimen in a petrie dish. The eye doc looked at my history and asked me several questions. He took out a "dry sanitizer" from a drawer, held it close to me and BAM the itchies came on in a fury. That was 2 years ago.
The skin is healed but we are still working on the eyelids. I have to wash my eyelids with baby shampoo, rinse completely and apply external antibiotics. I am just starting to see some progress. It is slow healing because eyelids don't have a whole lot of blood flow.
If anyone is getting the itchies from being around fabrics, the formaldehyde is causing it.