Sensitization of mouse skin to X irradiation by moderate heating

The combined effects of heat and x irradiation have been studied on mouse skin using skin reactions on the feet. The skin was heated for one hour by immersion in a water bath at temperatures ranging from 25.5-43.5 degrees C. When the x irradiation was in the middle of this heating period a thermal sensitization to the x-ray damage was observed. The effect increased with temperature above 39.5 degrees C and doubled the effectiveness of the x rays at 43.5 degrees C. When the heating and irradiation were not concurrent the timing and sequence of treatments were important. Heat before irradiation was more effective than heat after irradiation, particularly if the interval was three hours or greater.