Cold Showers: The Evidence
**The Famous Study:** Cold showers may reduce sick days by about 29%[1].
Cold water immersion has documented effects on mood and wellbeing[2][3].
How Cold Showers Work
- Triggers the sympathetic nervous system ("fight or flight")
- Releases norepinephrine and cortisol
- Increases heart rate and blood pressure temporarily
- May improve circulation over time
Practical Protocol (from the RCT)
The Dutch study used this protocol:
- Regular warm shower first
- End with 30-90 seconds of cold water
- As cold as tolerable
- Daily for 30 consecutive days
Hot vs Cold for Recovery
Contrast water therapy (alternating hot and cold) may help with muscle recovery[4].
For exercise recovery:
- Cold – May reduce inflammation and muscle soreness
- Hot – Helps relax muscles and improve blood flow
- Contrast – Alternating may combine benefits
Water therapy (hot or cold) can be beneficial for rehabilitation[5].
Safety Considerations
**Warning:** Extreme cold water (below 4°C/39°F) can be dangerous[6].
Cold showers are generally safe for healthy adults, but avoid if you have:
- Heart conditions or arrhythmias
- High blood pressure (uncontrolled)
- Raynaud's disease
- Recent illness or fever
Start gradually – the Dutch study allowed participants to build up tolerance over time.
Shower Frequency
There's surprisingly little high-quality research on optimal shower frequency. General guidance from dermatologists:
- Daily showers – Generally fine for most people
- Every 2-3 days – May be better for dry skin
- Over-washing – Can strip natural oils from skin
- Hot water – More drying than lukewarm
Individual needs vary based on activity level, climate, and skin type.
Common Claims
**Supported:** Cold showers increase alertness and mood (temporarily) – the stress response releases norepinephrine.
**Supported:** Warm baths/showers before bed can improve sleep[7][8].
**Overstated:** "Cold showers boost immune system" – The Dutch study found fewer sick days, but this could be behavioral (people who take cold showers may be more health-conscious overall). The immune mechanism isn't proven.
**Overstated:** "Cold showers burn significant fat" – While cold exposure does activate brown fat, the calorie burn from a brief cold shower is minimal.
References
- Buijze GA, Sierevelt IN, van der Heijden BCJM, et al. (2016). The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial. PLOS ONE. [DOI]
- Cain T, et al. (2025). Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis. PLOS ONE. [DOI]
- Various (2019). Cortisol levels after cold exposure are independent of prior habituation. PLOS ONE. [DOI]
- Various (2013). Contrast Water Therapy and Exercise Induced Muscle Damage: A Systematic Review. PLOS ONE. [DOI]
- Various (2022). Does aquatic physical therapy affect the rehabilitation of chronic diseases?. PLOS ONE. [DOI]
- Various (2025). Single immersion in cold water below 4°C: A health hazard review. PLOS ONE. [DOI]
- Various (2022). A review of Japanese-style bathing: its demerits and merits. Journal of Physiological Anthropology. [DOI]
- LJMU Research (2018). A shower before bedtime may improve sleep onset latency of youth soccer players. LJMU Repository.