Working out strengthens your body, fortifies your bones, and improves your immune system. But don't forget that as you sweat, your pores are opening, making you more prone to outside invaders slipping in through your skin. Problem is, many of the trendy exercise clothes are made from chemically treated fabric that, yes, when we sweat can be purged. Why work so hard to be healthy, all the while swaddling ourselves with something so potentially unhealthy?

Beyond the immediate concern of our bodies, the chemicals used in the production and manufacturing of exercise clothes are unhealthy to the planet. Take, for example, a favorite fabric loved for its comfort and "purity"—conventionally grown cotton. In case you don't know, let me fill you in on the facts: