"When there aren't better ones about." He tilts his head slightly, focusing his magic into First Aid - a golden scrawl of script in math-like forms spreading itself into a seal under him, then a little burst of golden light from his raised hand to the burned arm.

The spot is a little pink, but a little faded. Like a sunburn that's ready to peel. Sorry dude, you can deal with that part on your own.

"... Won't last due to increased healing speed, or some absorption of elements?" Those were the two things he could think of, so it's said with some absent-minded curiousity.