Both dryer sheets and fabric softeners contain chemicals known to be toxic to people after sustained exposure. Dryer balls usually come as a set of three or six felted wool balls that you put in the dryer with your laundry. By bouncing around with the drying items, they work to separate layers and create air pockets to help fluff, soften, and reduce drying time.
Read more on this from Scientific American and Treehugger.com.
Photo by Susan O'Donnell