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Do cold plunges and ice baths boost your immune system?

What you hear: “Regular ice baths or cold plunges boost your immune system, speed up your metabolism and lift your mood.”

What the studies found

A 2025 review of 11 trials (3,177 healthy adults) found stress was lower 12 hours after cold water, but not at other time points, and inflammation rose straight after. Immune measures did not change and mood did not improve. In the largest trial, 3,018 Dutch adults ending showers with 30 to 90 seconds of cold took 29% fewer sick days off work, but were ill on just as many days. Metabolism claims have not been tested in these trials.

Take care: Sudden immersion in cold water triggers a cold shock response that can lead to drowning or heart rhythm problems, so people with heart disease should check with a doctor first.

What you could do

A short cold shower is a safe, cheap thing to try if you like how it feels; skip plunges alone or if you have heart problems.

See it in the habit library, with what it means for your own longevity score.

Not medical advice. General information from published studies, not a diagnosis or a treatment plan. Talk with your doctor before starting a supplement or changing a medicine, especially if you are pregnant, take other medicines or have a health condition.

How we judged it

Not proven: Not enough good human evidence yet, either way. We judge the claim as it is usually said online, not the habit itself. Trials assign people at random, so they can show cause; observed studies follow people and show a link, not proof. Last checked: October 2026.

The studies, in their own words

1. Cain et al. PLoS One 2025

   While meta-analysis showed no significant effects on immune function immediately (SMD: -0.16 [95% CI: -0.82, 0.51], p > 0.05) or 1 hour (SMD: -0.18 [95% CI: -1.09, 0.74], p > 0.05) post-CWI ... Improvements were also observed in sleep quality and quality of life, but not mood.

2. Buijze et al. PLoS One 2016

   A routine (hot-to-) cold shower resulted in a statistical reduction of self-reported sickness absence but not illness days in adults without severe comorbidity.

3. Tipton et al. Exp Physiol 2017

   we look at the history of CWI and examine CWI as a precursor to drowning, cardiac arrest and hypothermia.

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