Don’t force yourself into cold showers to “boost immunity”

In a trial of 3018 people, those who took cold showers had 29% fewer sick-leave occasions. But the total days of leave matched everyone else, so it does not mean less illness. A 2025 pooling of 11 trials found that after cold water, markers of inflammation rose briefly and immune markers did not change. Wash if you like; just do not treat it as a health investment.

Cost

No money. You have to endure 30 to 90 seconds of discomfort each day; sticking with it in winter takes willpower. People with cardiovascular disease should also be careful: cold stress is a risk for them.

Benefit

A Dutch randomized controlled trial enrolled 3018 people who, after a hot shower, rinsed with cold water for 30, 60, or 90 seconds. Their sick-leave occasions fell by 29% (IRR 0.71, a rate ratio for counts). But the paper states there was “no significant between-group difference in sick-leave days”: total days ill were the same on both sides. Quality of life, work productivity, and anxiety also showed no meaningful differences. A 2025 systematic review pooled 11 randomized trials and 3177 people. Right after cold water and 1 hour later, markers of inflammation rose instead. Immune markers did not change. Stress fell only at the 12-hour time point. The authors themselves say the evidence is “limited by few RCTs and small samples,” meaning such randomized trials are scarce and each enrolls few people. It looks worthwhile because it costs nothing and the intuition “suffering works” is smooth.

Notes

Controversy: Sick-leave occasions did fall by 29%, and that gap does not look like chance. But total days of illness did not fall, so you cannot say people truly got sick less. Cold water for athletes’ recovery after training is a different question; this item does not cover it. Cold showers show no clear harm in healthy people; just do not treat them as a health investment.

Sources · 2

1. Buijze GA et al. (2016). The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial. PLOS ONE. doi.org/10.1371/journal.pone.0161749
2. Cain T et al. (2025). Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis. PLOS ONE. doi.org/10.1371/journal.pone.0317615