Infection and sauna

Infection and sauna concerns the movement of infectious agents in the hot room — a question of aerosol and contact hygiene rather than of the heat itself. The cabin is warm, damp, crowded and shared: coughs and sneezes travel in the steam, hands and towels touch the benches, buckets and ladles, and bare feet walk the wet floors. The myths that belong here are symmetrical — that the heat "kills germs" and that the sauna "spreads everything" — and the honest account is the middle one: ordinary hygiene prevents most transmission, the febrile and the coughing stay away, and the cabin's own heat plays no sterilising role in the timescale of a session.

The routes of transmission

The respiratory viruses that cause common colds, flu and other winter infections are shed from a cough or a sneeze and can survive on hands and surfaces for many hours, as national guidance on colds spells out; in a small, humid, actively breathing room the aerosol route is the efficient one, and the benches, the door handles, the water ladle and the shared towels are the contact route (see Common cold and sauna). The skin and foot side is the other chapter: fungi of the feet and skin infections travel on warm, damp floors and benches, which is why the fixed rules of the cabin include the towel beneath the body, the shower before and after, and the dry, ventilated path through the facility (see Sauna hygiene, Sauna floor and Sauna floor drain). Who is infectious is the decisive filter: the person with a cough, a runny nose or — unreservedly — a fever (Fever and sauna) has no place on the bench, and NHS guidance on both fever and colds is explicit that the unwell stay at home and avoid contact until the symptoms are gone; the immune system's own role and the claims that bathing "boosts" it are assessed under Immune system and sauna.

The "sterilising heat" claim and its limits

The claim that "the heat kills bacteria" circulates in sauna marketing and deserves the full answer. Heat does kill microorganisms — at sufficient temperatures for sufficient contact times — but the air of a cabin is at the temperature of the air, not of the skin, droplets survive humid heat well within plausible times, and the contact surfaces of a cabin (wood, towel, floor) are neither sterile nor sterilised during a session of ordinary use. Disinfection of facilities is a cleaning-schedule question with its own proper standards (see Cleaning a sauna, Commercial sauna cleaning and the Sauna maintenance schedule), not a property of the steam; and the "sauna kills viruses" line has never survived the simple epidemiological observation that respiratory infections transmit in sauna-using populations like infections everywhere (see Air quality monitoring in a sauna for the ventilation side).

The practice rules

The practice rules assemble themselves: no bathing while febrile or with an active respiratory infection; stay away for a day or two after the symptoms clear; shower before entering (the body's own hygiene resets the skin flora, see Skin and sauna); sit and lie on a towel; do not share the ladle, bucket or cups; wash hands after the session; and dry thoroughly — the mycologist's corner of the cabin is the damp fold, not the dry bench. Commercial facilities' responsibilities — the cleaning regime, the floors, the shared items, and supervision that keeps the visibly unwell out of the hot rooms — are developed under Sauna supervision, staff safety and the facility's own Sauna risk assessment (see also older, young and immunocompromised bathers for the groups with the least margin).

The summary

The summary is the hygiene rulebook in one sentence: the sauna transmits what people bring in, the healthy bather who washes, towells and stays home when ill is the decisive element of its microbiology (see Sauna and health and Using a sauna).

See also

• Fever and sauna
• Sauna hygiene
• Commercial sauna cleaning
• Common cold and sauna
• Immune system and sauna

References

• National Health Service. "Common cold." NHS, UK. nhs.uk/conditions/common-cold (page reviewed 22 March 2024)
• National Health Service. "High temperature (fever) in adults." NHS, UK. nhs.uk/conditions/fever-in-adults (page reviewed 24 May 2023)
• Kukkonen-Harjula K, Kauppinen K. "Health effects and risks of sauna bathing." International Journal of Circumpolar Health 65(3):195–205, 2006. doi:10.3402/ijch.v65i3.18102
• Hussain J, Cohen M. "Clinical effects of regular dry sauna bathing: a systematic review." Evidence-Based Complementary and Alternative Medicine 2018:1857413, 2018. doi:10.1155/2018/1857413
• Laukkanen JA, Laukkanen T, Kunutsor SK. "Cardiovascular and other health benefits of sauna bathing: a review of the evidence." Mayo Clinic Proceedings 93(8):1111–1121, 2018. doi:10.1016/j.mayocp.2018.04.008