When the body is hot, a person starts sweating. The body has certain heat, so invisible heat qi is always dispersed from the body. When the heat of the body exceeds certain level, heat qi changes its shape to the liquid state, sweat. This is because heat qi is too strong to disperse in the state of gas. When heat qi becomes stronger, the body cannot disperse all the heat in perspiration, the liquid state, so the body tries to discharge it in the solid state. That is the state of eczema. The reason why eczema is red is because of heat in the body.
*This article is translated from "Yamai hitokuchi Memo" written by Shoji Kobayashi, 2005.