The important factors for UV sensitivity in humans are considered to be the skin pigmentation and the epidermal thickness. In this study on 73 Caucasians (age 20-85 years), we investigated in UV unexposed buttock skin the relationship between the UV sensitivity and constitutive skin pigmentation and thickness of the stratum corneum and the cellular part of the epidermis, in 34 normal people and in 39 skin cancer patients (20) patients with cutaneous malignant melanoma and 19 patients with basal cell carcinoma of the skin). Skin pigmentation was measured by skin reflectance spectroscopy, and UV sensitivity by phototest with a solar simulator. Thicknesses of the stratum corneum and the cellular part of the epidermis were determined by light microscopic evaluation of skin biopsies from the phototest areas. We found that epidermal thickness was independent of skin type and was not correlated to constitutive skin pigmentation. Thickness of the stratum corneum was statistically not different in normal persons and in skin cancer patients (P = 0.41) and was independent of gender (P = 0.61) and age (P = 0.56), while thickness of the cellular epidermis decreased with age (P < 0.01). Stratum corneum thickness was found to be of minor importance for the constitutive UV sensitivity (accounting for on average 11% of the total photoprotection), which was mainly determined by the constitutive skin pigmentation (goodness-of-fit for correlation r = 0.83). A theoretical model for the relationship of UV dose to induction of clinical erythema grade and skin pigmentation and thickness of the stratum corneum was developed. Objective measurements of skin pigmentation in UV unexposed skin by skin reflectance spectroscopy in Caucasians, normal people and people with cutaneous malignant melanoma and basal cell carcinoma of the skin predicts the constitutive UV sensitivity with a high degree of precision.

It is found that thickness measurements of the stratum corneum and the cellular epidermis are reliably performed on cryostatic cut sections stained with haematoxylin-eosin.

Frequent exposure to water is an important risk factor for the development of irritant hand eczema. Evaluation of cream efficacy in protecting against water is difficult. A new non-irritant, non-invasive method is introduced, based on evaluation of colour intensities when an aqueous solution of crystal violet is applied to the skin, after pretreatment with different creams. By skin reflectance measurement, differences in colour intensity were objectified. Measurements of transepidermal water loss were also performed, 2 barrier creams and a moisturizer were tested on the dorsal and volar aspects of the hands. One barrier cream contained silicone, the other solid particles. The moisturizer had a high content of lipid. In one experiment, the immediate effect of the creams in protecting against water was evaluated. In a second experiment, the water resistancy of the creams was tested, using a standardized water immersion procedure (4 x 20 min). The barrier cream with particles gave the best immediate protection (dorsal 76%, volar 69%). The moisturizer was intermediately protective (dorsal 57%, volar 34%), while very little protection was found for the silicone-containing cream (dorsal 16%, volar 10%). The water immersion procedure resulted in only minor changes in protection for each cream. When comparing transepidermal water loss in the treated areas with pretreatment values, a reduction was recorded only for the particle-containing barrier cream. The colour method described may be used as a quick and easy test of the protective effect of creams against water.