Speaking from experience, Petryszyn says to use household ammonia to neutralize the proteins. The combination of heat and ammonia-like qualities from urine does a swell job of easing that searing, throbbing pain. And even if it doesn't, it makes for one helluva cocktail party segue. The bottom line is, unless you have some allergic reaction, the wrath of the ray poses no mortal danger. And if you do get hit, and none of the above remedies suffice, consider buying a fresh catch off a local fisherman and eating the little bastard.
Revenge is sweet.