Ibn Sina in his Canon said, “Sleep induces sweating. It does this by a process of overcoming the effete matter, and not by a process of continuous dispersal of attenuated matter. When a person sweats heavily during sleep, without obvious cause, nutrients accumulate in excess of the bodily requirements ; when sleep encounters matter adapted for digestion and maturation, it turns it into the nature of blood and warms it, and in consequence innate heat is engendered, and travels through and warms the whole body. “