Hypohidrosis in Individuals with Exertional Heat Injury: A Prospective Open Cohort Study

Hypohidrosis is a risk factor for developing heat-related illnesses.

To determine the prevalence of hypohidrosis in heat injury.

Soldiers from the Singapore Armed Forces who developed heat injury between January 1, 2012 and December 31, 2013 were invited to participate in the study. Subjects were induced to sweat through exercising in a temperature- and humidity-regulated room, and then atomized starch-iodine powder was administered over their whole body to detect hypohidrosis. If this was found to be present, investigations to elucidate the cause of anhidrosis were performed.

Out of 65 males, 30 consented to participation. One was excluded because an exogenous cause resulted in heat injury. Nine (31%) demonstrated hypohidrosis. Of these, 1 (11%) had miliaria profunda, 2 (22%) had acquired idiopathic generalized anhidrosis and 6 (67%) manifested a new phenotype which we termed acquired symmetrical hypohidrosis (ASH).

Thirty-one percent of healthy soldiers who developed heat injury had hypohidrosis. Concurrently, a new clinical phenotype of ASH was identified.