Knit Hats.

I was informed today that we were no longer allowed to wear our knit hats "on the floor" and we're only allowed in the meat coolers and freezer. I work in the meat department. I was wondering if I could get a medical exemption due to my alopecia totals. Another words, I can't grow any hair so I am going to be freezing. I am allowed to wear my baseball style hat, but it isn't warm enough and my department manager tells me to just get used to it. Why did the company sell this to us if it is against company policy to wear these style hats in the first place?