Erythema and skin blood content

Abstract
SUMMARY: We have studied the inflammatory response produced by painting pigs and hairless mice with anthracene and subsequently exposing the skin to fluorescent blacklight lamps. Erythema and oedema appeared in pig skin shortly after the onset of irradiation; oedema but no erythema was evident in mouse skin. The response in both animals became increasingly severe as long as irradiation continued, and began to resolve when irradiation ceased. Hyperaemia (increased tissue blood content) was quantified by the increase in 51Cr-RBC content (c.p.m./wet weight) of the skin. Erythema (appearance of redness) was assessed by the use of an ‘erythema grading scale’ consisting of red gelatin filters of increasing red saturation sandwiched between clear acrylic sheets. Mouse skin responded with a nine-fold hyperaemia compared with unirradiated skin, although no erythema was produced. In contrast, pig skin responded with intense erythema with no corresponding increase in hypaercmia. It is apparent that a stimulus which produces hyperaemia will not necessarily produce erythema, and erythema can develop without hyperaemia.