How do a substance that evaporates quickly can numb the skin like the ethyl chloride?

Our chemistry professor told us its has to deal with the kinetic molecular theory, with the properties of solid and liquids?|||An evaporating substance uses the heat from the skin to evaporate therefore leaving the skin cold and consequently numb.|||any evaporating substance will draw heat from its surroundings as it does so.I believe this is called an endothermic reaction.if this process is taking place on your skin it will leave the skin feeling numb from the heat loss.