Do cold showers stop you getting ill?

Not according to the main trial, which found fewer sick days taken from work but no difference in days ill.

How long should the cold part last?

In the trial, 30, 60 and 90 second cold finishes gave similar results, so longer was not shown to be better.

Do cold showers count as cold water immersion?

They are a milder, different exposure. The muscle soreness research used immersion, so do not assume the same effect.

Should I check with a doctor first?

If you have a heart or blood pressure condition, Raynaud's or are pregnant, yes. The trial involved healthy adults aged 18 to 65 without severe illness.

Cold Showers: What the Evidence Says

The strongest trial on cold showers found that people who ended their daily shower with 30 to 90 seconds of cold water took about 29% less sickness absence from work over the period studied, but were not ill on fewer days. The effect is modest, self-reported and unproven as a health treatment. A cold shower is a low-cost way to try cold exposure, not a substitute for medical care.

The main trial, in plain terms

The study was published in PLoS ONE in 2016 by Buijze and colleagues in the Netherlands. It was a randomised controlled trial of 3,018 adults aged 18 to 65 with no severe comorbidity and no previous routine cold showering. They were randomly assigned to four groups. Three groups finished a hot shower with cold water for 30, 60 or 90 seconds every day for 30 days. The control group did not. Afterwards the cold shower groups could continue for 60 more days if they chose.

About 79% of the cold shower participants completed the 30-day protocol. Sickness absence from work was 29% lower in the cold shower groups than in the controls (incidence rate ratio 0.71, P = 0.003). There was no significant difference between groups in the number of days people reported being ill. No serious adverse events were reported.

How to read those results

The headline is easy to over-read. Participants felt ill as often as the controls. What changed was how often they stayed off work. The researchers did not establish why, and a summary from the British Psychological Society Research Digest says the mechanism is speculative, with hormonal effects or simply the benefit of brief daily physical activity among the suggestions. It also reports that cold showers did not provide immunisation against illness as such.

Sickness absence was self-reported, and participants could not be blinded to whether they were taking cold showers. People who sign up to a cold shower challenge may feel more committed to showing up. The trial was run in the Netherlands, and it tested a shower, not full immersion in a tub or the sea.

Outcome in the trial	Result	How firmly it can be read
Work absence due to sickness	29% lower in cold shower groups	Self-reported, not blinded
Days ill	No significant difference	Cold showers did not appear to prevent illness
Serious adverse events	None reported	Healthy adults aged 18 to 65 with no severe comorbidity
Energy and wellbeing	Higher energy reported by participants	Self-reported; quality of life gains faded when re-measured, per the BPS summary
30 versus 60 versus 90 seconds	Similar results reported	Shorter bursts appeared enough in this trial

Cold shower versus cold water immersion

A shower and an immersion are different stimuli. In a plunge or a sea swim, most of your body goes into the water at once, and the Irish Coast Guard, Water Safety Ireland and the RNLI warn that cold water shock can occur in water below 15°C. A shower rarely produces the same sudden full-body response, but no Irish source consulted for this article measures the risk of shower-based cold exposure, so it is not safe to say it is risk-free for everyone.

The muscle soreness findings that support ice baths used immersion, so do not assume a shower gives the same recovery effect. Our comparison of ice bath, cold plunge and cold shower goes through the differences, and what is cold water immersion covers the basics.

Who should check first

The trial included healthy adults, so it says little about people with health conditions. The American Lung Association notes that cold water narrows blood vessels, raising blood pressure and making the heart work harder, and that most healthcare providers advise against cold plunges for people with heart conditions. That concern applies to full immersion, but anyone with heart disease, high blood pressure or an irregular heartbeat should ask a GP before starting any deliberate cold exposure, including showers.

The HSE describes cold as the usual trigger for Raynaud's phenomenon, with an example of putting hands under a cold tap. If your fingers or toes turn white or blue in the cold, see a GP before making cold showers a habit. The same goes for pregnancy, and for anyone unsure. See also who should not do cold water immersion.

A sensible way to try it

Finish your normal warm shower first, as the trial did, then turn the temperature down for the last 30 seconds.
Keep your breathing slow and steady. If you gasp or feel dizzy, turn the water warm again and stop for the day.
Build up gradually. The trial found 30, 60 and 90 seconds gave similar results, so there is no evidence you need to go longer.
Dry off and dress warmly straight away, especially in a cold bathroom.
Stop if you notice chest pain, palpitations, numb fingers that do not recover or any symptom that worries you, and speak to a GP.

If your aim is to feel more awake in the morning, the self-reported energy findings suggest cold showers may help some people. If your aim is to avoid colds, the evidence does not support that. And if you later move on to open water, treat that as a separate step with its own safety routine, beginning with the cold water safety checklist.