People who wear leggings are looking for a stretchable fabric with breath ability to keep your legs safe. There are many different fabrics used in making leggings, with a combination of spandex among them. Spandex is to provide that stretch fit and freedom that you can have while wearing leggings. Spandex is combined with polyester or cotton or other fiber to provide you the fabric for using in leggings. Of course, in terms of breath ability and comfort, a combination involving cotton would be a blessing to your skin. But if you are looking for workout needs, then a combination with polyester is the best bet.