If you want to be absolutely sure of liquids not freezing you need to wear it under all major insulating layers. My contact lense liquid (essentially just salty water for cleaning the lenses) froze in the inner pocket of my snowmobile suit. That pocket is on the INSIDE of my snowmobile jacket. You should think that my snowmobile suit should be warm enough, but beneath that layer was several more layers of insulation (my snowmobile bib, my fleece sweather as well as wool underwear). . I was snug and warm in -30 C, the contact lens fluid was evidently not. Since then I've always carried essential can't-freeze items in a small pouch under my middle layer.