Previously covered: lip-chap is the stuff you put on to prevent sore lips.
Skin-chap is the soreness that happens when you don't dry your hands well in the winter cold.
August is obsessed with drying his hands. He rubs each little space between his fingers and howls if you rush him out of the bathroom before he's had his two solid minutes of drying-time. "No! I'll get skin-chap what will make my hands hurt!"