Environmental influences on UVB erythema

In 31 volunteers the superficial skin temperature of one forearm was either raised or lowered by a warm or cold water bath. Immediately afterwards the individual minimal erythema dose (MED) for monochromatic light of 300 +/- 5 nm (UVB) was determined on both arms. Compared to the control forearm, a warm water bath significantly lowered the MED (p less than 0.001), whereas a cold water bath had no influence on the light sensitivity. In 14 volunteers the MED for polychromatic UVB was determined on the lower back with and without a continuous cold air flow 5 min before and during the UVB exposure. The continuous cold air flow significantly increased the MED (p less than 0.05). Environmental factors such as warm water or cold air have modulating effects on UVB erythema. These interactions should be considered when dealing with the effects of natural sun exposure or phototherapy.