The pathogenesis of miliaria rubra. Role of the resident microflora.

Anhidrosis was induced in volunteers by covering the skin with an impermeable plastic film. The degree of sweat suppression and miliaria after a thermal stimulus was directly proportional to the increase in the density of resident aerobic bacteria, notably cocci. No anhidrosis resulted when antibacterial substances were used to prevent the expansion of the microflora. Histological study showed a PAS-positive diastase resistant amorphous mass deep within the acrosyringium after 2 days of occlusion, accompanied by a periductal dermal infiltration of leukocytes. After another 2 days the duct became clogged by an amalgam of degenerating leukocytes. This impaction sloughed after about 3 weeks as a result of epidermal renewal. Colonies of bacteria were never found within the ducts. It is postulated that cocci secrete a toxin which injures luminal cells and precipitates a cast within the lumen. Infiltration by leukocytes creates an impaction which completely obstructs the passage of sweat for several weeks.