SUNBURN 523 



There is a widely accepted opinion that wet or perspiring skin is more 

 susceptible to sunburn than dry skin. This was investigated by Blum 

 and Terus (194()b), but no significant difference was found in the ery- 

 themal threshold for skin wet with water from that for dry skin. Simi- 

 larly, subjects showed no significant difference in threshold before and 

 after profuse sw^eating in a "hot" room. I find a clue to the origin of this 

 particular idea in a personal experience. A number of years ago I 

 received a severe sunbiu'n after an excursion in a small boat, during the 

 whole of which I thought myself protected by a white shirt I was wearing. 

 There were intermittent show^ers with bright sunlight between, and the 

 sea w^as choppy so that my shirt and skin were drenched during most of 

 the day, either from rain or spray. I remember that some additional pro- 

 tection was offered by my undershirt which was also wet but under which 

 the sunburn was less severe. I might have concluded that wetting the 

 skin had lowered the erythemal threshold so that I sunburned through the 

 shirt which I knew would have afforded adequate protection under other 

 circumstances. The alternative answer was, of course, that the trans- 

 mission of the erythemal radiation by the shirt was increased by wetting. 

 Support for the latter idea came some years later from tests of the pro- 

 tection afforded against sunburn by fabrics (Blum and Terus, 1946b), 

 when it was found that various kinds of white shirtings became much 

 more transparent to the erythemal radiation when wet, presumably as a 

 result of diminished scattering by the wet fibers. 



The wide differences in individual erythemal thresholds, the variation 

 of the threshold in a given individual, and the failure to evaluate correctly 

 the amount of exposure to erythemal radiation in sunlight, are factors 

 which no doubt contribute to the variety of opinions encountered regard- 

 ing the efficiency of a given sunburn preventive. These factors, and the 

 misconceptions regarding tanning, may account for many apparent 

 vagaries of sunburn. In these pages I hope I have explained away a 

 number of false ideas, but I have also taken the risk of introducing a few 

 more by some of my speculations regarding the mechanism of sunburn 

 (particularly in the scheme in Fig. 13-11). So, in ending, I should call 

 attention to the need for further study of the sunburn process, always with 

 proper regard for the knowai physical and physiological aspects of the 

 problem lest we be led further into the realm of fancy. 



REFERENCES 



Arnow, L. E. (1937) The formation of dopa by the exposure of tyrosine solutions to 



ultraviolet radiation. J. Biol. Chem., 120: 151-153. 

 Baumberger, J. P., V. Suntzeff, and E. V. Cowdry (1942) Methods for the separation 



of epidermis from dermis and some physiologic and chemical properties of isolated 



epidermis. J. Natl. Cancer Inst., 2: 413-423. 

 Blum, H. F. (1941a) Photodynamic action diseases caused by light. Reinhold 



Publishing Company, New York. 



