Wrinkle-free sheets may seem like a revolutionary convenience, but they may actually be preventing you from getting a good night's rest. Poly-blend cotton sheets that are "wrinkle-free" often have finishes on the fabric that release formaldehyde. The chemical can be an irritant that bothers your throat and eyes. Look for organic, 100 percent cotton sheets instead. If you want them to look pristine without the hassle of chemicals or using an iron, just take them out of the dryer when they are still hot. This will prevent wrinkles from setting.