{"title":"Sweat evaporation in humans: A molecular and thermodynamic perspective.","authors":"Edward T Ashworth","doi":"10.1113/EP093011","DOIUrl":null,"url":null,"abstract":"<p><p>Evaporative heat loss through sweating is essential for maintaining thermal balance in humans, particularly during exercise or in hot environments. Although the physiological mechanisms regulating sweat production and skin blood flow are well documented, the molecular processes underpinning sweat evaporation are less often considered. This review explores the physics of sweat evaporation from first principles, examining how energy is transferred, how water molecules escape the liquid phase and how this process is shaped by local and systemic factors. At the molecular level, evaporation occurs when surface water molecules attain sufficient kinetic energy to overcome hydrogen bonding. The energy required for this phase change, the latent heat of vaporisation, is supplied via conduction from the skin and, ultimately, from core body heat. The molecular energy within the sweat layer follows a Boltzmann distribution, meaning that only a subset of molecules have sufficient energy to evaporate at any time. As these high-energy molecules escape, the remaining sweat cools, helping to lower body temperature. This process continues as long as heat is resupplied via skin blood flow. Environmental conditions, such as humidity, airflow and clothing, affect the likelihood that evaporated molecules will remain in the vapour phase, while electrolytes in sweat can slightly reduce vapour pressure by locally altering the bonding structure of water. These factors determine how effectively sweat can evaporate by influencing surface area and liquid retention. By linking classical thermodynamics to human physiology, this review presents a unified framework for understanding how molecular interactions, statistical physics and environmental conditions converge to influence heat loss.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8000,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Experimental Physiology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1113/EP093011","RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Evaporative heat loss through sweating is essential for maintaining thermal balance in humans, particularly during exercise or in hot environments. Although the physiological mechanisms regulating sweat production and skin blood flow are well documented, the molecular processes underpinning sweat evaporation are less often considered. This review explores the physics of sweat evaporation from first principles, examining how energy is transferred, how water molecules escape the liquid phase and how this process is shaped by local and systemic factors. At the molecular level, evaporation occurs when surface water molecules attain sufficient kinetic energy to overcome hydrogen bonding. The energy required for this phase change, the latent heat of vaporisation, is supplied via conduction from the skin and, ultimately, from core body heat. The molecular energy within the sweat layer follows a Boltzmann distribution, meaning that only a subset of molecules have sufficient energy to evaporate at any time. As these high-energy molecules escape, the remaining sweat cools, helping to lower body temperature. This process continues as long as heat is resupplied via skin blood flow. Environmental conditions, such as humidity, airflow and clothing, affect the likelihood that evaporated molecules will remain in the vapour phase, while electrolytes in sweat can slightly reduce vapour pressure by locally altering the bonding structure of water. These factors determine how effectively sweat can evaporate by influencing surface area and liquid retention. By linking classical thermodynamics to human physiology, this review presents a unified framework for understanding how molecular interactions, statistical physics and environmental conditions converge to influence heat loss.
期刊介绍:
Experimental Physiology publishes research papers that report novel insights into homeostatic and adaptive responses in health, as well as those that further our understanding of pathophysiological mechanisms in disease. We encourage papers that embrace the journal’s orientation of translation and integration, including studies of the adaptive responses to exercise, acute and chronic environmental stressors, growth and aging, and diseases where integrative homeostatic mechanisms play a key role in the response to and evolution of the disease process. Examples of such diseases include hypertension, heart failure, hypoxic lung disease, endocrine and neurological disorders. We are also keen to publish research that has a translational aspect or clinical application. Comparative physiology work that can be applied to aid the understanding human physiology is also encouraged.
Manuscripts that report the use of bioinformatic, genomic, molecular, proteomic and cellular techniques to provide novel insights into integrative physiological and pathophysiological mechanisms are welcomed.