ok, well it doesn't make sense to me, from a first aid point of view, that he recommends cool compresses and moisturizers, but a lukewarm bath.
i think he might have been trying to say that the oatmeal is good, but should have thought out the heat thing better. lukewarm is warmer than room temp, which would add more radiative energy (this time as direct heat) to the affected area, increasing discomfort and cellular damage. you can actually induce heat stroke if a person's core temp doesn't decrease enough. in other words, you don't put a person with a sunburn in a warm room. you cool them off as best possible, both internally with cool drinks, and externally, with cool water.
just my 2 cents.
in nomine patri, et fili, et spiritus sancti.
Meh nom eh noh...doot dooooo do do do.