Evidence that cold-water swimming prevents respiratory illness remains inconclusive.
Cold-water swimming triggers substantial cardiovascular, hormonal, and metabolic responses, but evidence that it prevents respiratory illness remains limited and inconsistent. A narrative review evaluated proposed benefits and established risks of winter swimming and cold-water immersion.
The authors highlighted immune-marker studies showing changes in leukocytes, monocytes, cytokines, and oxidative-stress pathways. However, protocols varied widely, participant samples were generally small, and most experiments measured biomarkers rather than actual infections.
One frequently repeated observation came from a survey of 85 ice swimmers: 40 percent said that their upper respiratory infections had become fewer, milder, or shorter after they began winter swimming. This means 40 percent perceived an improvement; it does not demonstrate a 40 percent reduction in infection risk. The survey lacked a randomized control group and depended on retrospective self-report.
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The review also emphasized the acute hazards of cold-water immersion, including cold shock, hyperventilation, cardiovascular strain, hypothermia, and drowning risk. These hazards vary with water temperature, exposure duration, health status, acclimatization, and swimming conditions.
Cold-water swimming may have health and wellbeing benefits for some people, but controlled trials measuring medically verified respiratory infections are needed before it can be described as an infection-prevention strategy.