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

  • Moderate value
  • Evidence B
  • Saves money
  • Disputed
  • Free
  • Takes minutes
  • No willpower

In plain words

In a trial of 3018 people, those who took cold showers called in sick 29% less often, but the total number of sick days was the same as everyone else's, so it cannot be said they got sick less. A 2025 review that pooled 11 trials found that after a cold rinse, markers of inflammation in the body actually rose briefly, while markers of immunity did not change. Take them if you like them; just don't treat it as a health investment.

Cost

Free. It means 30 to 90 seconds of discomfort a day, and sticking with it in winter takes willpower. People with heart and blood vessel disease should be careful, since cold exposure carries risk for them.

What you get

A randomized controlled trial in the Netherlands enrolled 3,018 people, who finished a hot shower and then rinsed with cold water for 30, 60 or 90 seconds. They called in sick 29% less often (IRR 0.71, a ratio of counts). But the original states “no significant between-group difference in sick-leave days”: the total number of days ill was the same on both sides. No meaningful difference was seen in quality of life, work productivity or anxiety either. A 2025 systematic review pooled 11 randomized trials with 3,177 people. Right after cold immersion and 1 hour later, markers of inflammation in the body actually rose. Immune markers did not change. Stress was lower only at the 12-hour time point. The authors themselves say the evidence is “limited by few RCTs and small samples,” meaning there are too few randomized trials of this kind and each has few people. It looks like a good deal because it costs nothing and the intuition that “what hurts must work” is too smooth

Notes

Dispute: the 29% fewer sick calls is a real gap and does not look like chance. But the total days ill did not fall, so it looks more like “going to work even when sick” than truly getting sick less. Athletes using cold water to help recovery after training is a different question and not covered here. Cold showers do no harm to healthy people; just don't treat them as a health investment

Evidence grade
B : Supported by research but without a precise number, or based on small or single studies.
Sources
  1. Buijze GA et al. (2016). The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial. PLOS ONE. https://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. https://doi.org/10.1371/journal.pone.0317615

Translated from the Chinese original. Original book, section 6, tip 12. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer