The Science of Cooling During Sauna Sessions
Sauna bathing is associated with relaxation, cardiovascular conditioning, and stress reduction.
However, prolonged exposure to high heat also raises skin and genital temperatures. Research in reproductive physiology and thermoregulation shows that male reproductive organs are particularly sensitive to heat, which has led scientists to study whether localized cooling may help counteract thermal stress during or after sauna use.
This page summarises the current scientific understanding behind heat exposure, scrotal temperature, and cooling strategies, with a focus on what is known, what is promising, and what remains unproven.
Why Cooling Matters in a Sauna
Testicular temperature is biologically regulated
In healthy adult males, the testes are physiologically maintained at a temperature 2–4°C below core body temperature. This temperature gradient is essential for normal spermatogenesis.
When scrotal temperature rises toward core temperature levels, sperm production and function may be affected. This principle is well established across clinical, observational, and experimental research.
How Sauna Heat Affects Male Reproductive Biology
Sauna exposure increases scrotal temperature
Whole-body heat exposure—such as sauna bathing—raises skin temperature and can elevate scrotal temperature, especially during seated sauna use where airflow is limited.
Studies measuring scrotal or intrascrotal temperature show that heat exposure can rapidly reduce the temperature differential that normally protects sperm production.
Human studies: sauna use and sperm parameters
A prospective human study involving healthy men who undertook two sauna sessions per week (80–90°C, 15 minutes) over three months reported:
- Reduced sperm count
- Reduced sperm motility
- Altered mitochondrial and DNA-related sperm markers
Importantly, these effects were fully reversible after discontinuation of sauna exposure, and sex hormone levels remained unchanged.
Earlier studies also reported transient reductions in sperm movement and quality following sauna-induced heat exposure.
Observational evidence from daily life
In studies where men wore temperature sensors during normal daily activities, higher average scrotal temperatures were strongly associated with lower sperm concentration and total sperm count, with measurable declines observed per 1°C increase.
Proposed biological mechanisms
Researchers propose several mechanisms linking heat exposure to impaired sperm quality:
- Heat-induced cellular stress in germ cells
- Increased oxidative stress
- Disruption of sperm chromatin structure
- Impaired mitochondrial energy production
These mechanisms are discussed consistently across reproductive biology reviews.
What Research Says About Scrotal Cooling
Localized cooling can significantly lower scrotal temperature
Clinical measurements show that localized ice application to the scrotum can lower intrascrotal temperature by approximately 6–7°C during use.
This confirms that targeted cooling is capable of meaningfully altering the thermal environment of the testes.
Cooling devices and fertility research
Scrotal cooling has been investigated primarily in the context of male subfertility, using cooling patches or devices applied daily or overnight.
Across small clinical studies and feasibility trials:
- Localized cooling successfully reduced scrotal temperature
- Some studies reported improvements in semen parameters
- Long-term compliance and comfort were identified as key challenges
While these studies support the biological plausibility of cooling, the evidence base remains limited in size and scope, and results vary between populations.
Sauna and Cold Exposure: Contrast Therapy
Heat followed by cold immersion
Many sauna users combine heat exposure with cold water immersion or ice baths. Research into contrast therapy focuses mainly on cardiovascular and autonomic effects rather than reproductive outcomes.
Acute studies show that alternating sauna heat with cold immersion causes:
- Rapid changes in heart rate
- Blood pressure fluctuations
- Strong autonomic nervous system activation
These responses may contribute to perceived wellbeing, but they also introduce non-trivial physiological stress.
Evidence for health benefits
- Sauna bathing alone is associated (observationally) with reduced cardiovascular and all-cause mortality in large population studies
- Cold-water immersion may improve subjective wellbeing and stress adaptation in some individuals
However, both areas rely heavily on observational data and relatively few long-term randomized controlled trials.
Safety Considerations
Whole-body cold immersion risks
Sudden cold exposure can trigger a cold shock response, including rapid breathing, increased heart rate, and elevated blood pressure.
This may pose risks for individuals with cardiovascular disease or hypertension.
Localized cooling considerations
Localized ice or cooling packs generally avoid systemic cold shock but can still cause issues if misused:
- Skin irritation or cold burns
- Numbness masking tissue damage
- Circulatory stress in vulnerable individuals
Common clinical recommendations include:
- Avoiding direct ice-to-skin contact
- Limiting exposure duration
- Discontinuing use if pain or numbness occurs
What Is Not Yet Proven
There is currently no large-scale clinical research directly testing:
- Ice packs worn during sauna sessions
- Long-term fertility outcomes from sauna-specific cooling
- Optimal cooling duration or temperature during heat exposure
The existing evidence supports the thermoregulatory rationale, but not medical claims.
How This Science Is Best Interpreted
- Sauna heat can temporarily raise scrotal temperature and impair sperm parameters
- Localized cooling can measurably reduce scrotal temperature
- Some fertility-focused studies suggest potential benefits, but evidence is limited
- No cooling method has been proven to prevent or reverse fertility issues
Any cooling product should therefore be positioned as a comfort and thermoregulation aid, not a medical intervention.
Sources and Further Reading
- Garolla A et al. Sauna-induced spermatogenic impairment: reversible effects. Human Reproduction, 2013.
- Jung A, Schuppe HC. Influence of genital heat stress on semen quality. Andrologia, 2007.
- Mieusset R et al. Increase in scrotal temperature in daily life and its relationship to semen quality. Human Reproduction, 2005.
- Zorgniotti AW et al. Effect of scrotal cooling on testicular temperature. Fertility and Sterility, 1980.
- Shafik A. Role of scrotal cooling in the treatment of male infertility. Archives of Andrology, 1992.
- Rimmer M et al. Feasibility of a scrotal cooling patch in men with oligoasthenospermia. Pilot clinical trial protocol, UK.
- Tipton MJ et al. Cold water immersion: physiological responses and risks. The Lancet, 2017.
- Laukkanen T et al. Sauna bathing and cardiovascular health. JAMA Internal Medicine, 2015.
- Bleakley CM et al. Cold-water immersion and health outcomes: systematic review. Sports Medicine, 2025.