Cold showers reduce sickness absence but not the number of days people feel ill.
Ending a warm shower with a short burst of cold water may reduce sickness absence from work, but it does not appear to reduce the number of days people feel ill. Researchers randomized 3,018 employed adults without severe health conditions to continue their usual showers or finish each shower with 30, 60, or 90 seconds of the coldest available water for 30 consecutive days. Participants could continue cold showering at their discretion for another 60 days.
Across the 90-day study, the cold-shower groups reported 29 percent fewer days of sickness absence than controls (incidence rate ratio 0.71; p = 0.003). However, there was no significant reduction in self-reported illness days, which included days with symptoms of illness, a cold, or flu. Outcomes also did not differ among the 30-, 60-, and 90-second protocols.
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The contrast suggests that cold showers may have affected perceived energy, symptom intensity, or willingness to work while feeling unwell rather than preventing infections. The study was randomized and large, but it was unblinded, relied entirely on self-reports, and did not confirm respiratory infections or influenza in a laboratory. It should therefore be described as a reduction in sickness absence, not a 29 percent reduction in colds.