Do you prefer polyester products for your outdoor activities? Synthetic fibers such as polar fleece, polypropylene & polyester are made from petroleum. They cannot breathe, quickly feel clammy and build up stink, and can cause overheating. Synthetics are highly flammable. If you think wool is an itchy material, unwelcome against the skin, we introduce to you smooth, silky-soft merino wool. Merino is naturally hypoallergenic and safe to use for skin with eczema, allergies and sensitive skin.