A 33 year-old woman with local pruritus, burning, erythema, and edema within minutes after exposure to heat is described. With more extensive exposure to heat, she occasionally had transient palpitation, light-headedness and nausea. For provocation, when her forearm was exposed to water at 45 for 5 mintes, a lession identical to her spontaneously induced ones deveopled only at the area exposed to heat within a few minues.