Most yoga pants are made from synthetic materials like polyester, which is a relatively new material derived from plastics. Because of its source material, polyester is also known to be rather thick, with a heavy weave that's often not very breathable and can hold odours or even cause irritation in people with sensitive skin.

Because so many people have this reaction to the traditional polyester/polyester blend materials, it's worth doing the research on what would work best for you. Alternative fabrics are available, though often the more natural materials have less stretch, and are more of a trouser fit than the legging slim fit.

There are also materials that combine the comfort natural with the durability of a synthetic, and keep the legging-style cut.