Global warming, heat-related illnesses, and the dermatologist

Abstract

Global warming, provoked by the greenhouse effect of high levels of atmospheric gases (most notably carbon dioxide and methane), directly threatens human health and survival. Individuals vary in their capacity to tolerate episodes of extreme heat. Because skin is the organ tasked with heat dissipation, it is important for dermatologists to be versed in the physiology of cutaneous heat dissipation and cognizant of clinical settings in which the skin's thermoregulatory responses may be impaired. When the external temperature is lower than that of the skin, the skin releases internal heat through direct thermal exchange with the environment, a process that is aided by an expansion of cutaneous blood flow and eccrine sweating. Cooling through the evaporation of sweat is effective even when the external temperature exceeds that of skin. Many factors, including environmental and physiological (e.g., age and sex), and pathological (e.g., preexisting illnesses, disorders of eccrine function, and medications) considerations, affect the skin's capacity to thermoregulate. Identification of individuals at increased risk for heat-related morbidity and mortality will become increasingly important in the care of patients.

Keywords: Anhidrosis; Drugs; Heat illness; Skin blood flow; Sweat glands; Thermoregulation.

Fig. 1

Thermoregulatory pathway and sites of action by drugs that affect thermal responses.

Fig. 2

Heat index as perceived temperature in relation to humidity (reproduced from: https://www.weather.gov/safety/heat-index; accessed April 2, 2020).

Fig. 3

State of Missouri thresholds for wet bulb globe temperature (WBGT). As constructed, the WBGT is always lower than the temperature in direct sunlight. Charts such as the one shown can be used to correlate WBGT readings with the risk for a heat-related illness (reproduced with permission from the Missouri State High School Activities Association).