Hypoallergenic??? What does that mean??

Allergies are like onions, every layer you peel there is another one under it. I can see this comparison being true in every facet of my life as mom to J. Our current issue is socks!! J can't wear anything besides 100% cotton. She immediately starts scratching if she does, especially if there is polyester in it! I have recently learned, since she has to wear socks and shoes to school, that 100% cotton socks do not exist! I also learned this is because they wouldn't stay on your feet! Duh! So since she came home the other day and notified me that "she has to wear socks or she will get in trouble." I have been putting her in socks, but her feet are starting to look bad again. So this made me start thinking about another potential layer! Could her night time scratching be from the material her bed is made from on the inside?? Is she allergic to the fabric blends or do they just rub her wrong? Could she be allergic to the things the bed and couch are made from? Am I just grasping to figure this out? We have allergy covers for mattress and air purifiers. I know her pillow is hypoallergenic, but so are countless things that make her flare!! That word is an oxymoron!!!