TRANSMISSION OF UV‐RADIATION THROUGH HUMAN EPIDERMAL LAYERS AS A FACTOR INFLUENCING THE MINIMAL ERYTHEMA DOSE

Abstract

Abstract— The extent to which transmission of human Caucasian epidermis and stratum corneum influences the Minimal Erythema Dose (MED) was examined for UV‐B and UV‐C. Transmission correlated well with variations in MED for UV‐B and UV‐C that exist between individuals, as measured on the skin of the lower back and anterior upper leg. Regional differences of the MED that occur within the same individual between different parts of the body, were related less well to differences in transmission. For UV‐B, the difference in transmission of stratum corneum and epidermis between upper leg and lower back was on the average too small to completely account for the difference in MED UV‐B. Other parameters, therefore, have to be involved in determining such regional variations in MED UV‐B. For UV‐C, on average, the difference in transmission of stratum corneum was smaller and of epidermis larger than the difference in MED UV‐C between upper leg and lower back, though the deviations were not significant. A series of UV‐B irradiations of the lower back resulted in an increase in MED UV‐B and MED UV‐C, which was paralleled by a decrease in transmission of stratum corneum and epidermis. The average decrease in UV‐B transmission of stratum corneum was too small and that of epidermis somewhat too large to account for the average increase in MED UV‐B. The average decrease in UV‐C transmission of stratum corneum was about as large as the average increase in MED UV‐C. Consequences of these observations for the location of the primary reactions leading to erythema are discussed. The relationship between log MED UV‐C and log MED UV‐B was confirmed to be approximately linear.