Skin and sauna
Skin and sauna describes what the hot, moist room does to the largest organ of the body, and what the bather should do in return. The skin is the interface on which everything in the sauna acts first — the heat, the sweat, the steam and the wood — and the visible signs of bathing, the flush, the sheen and the glow, are skin phenomena. Its care is a matter of ordinary hygiene and simple product use, and its borderline with medicine runs through the chronic skin conditions treated in their own articles.
What the heat does to the skin
The direct effects of a sauna session on the skin are mechanical and vascular rather than mysterious. The skin vessels dilate in the heat (see Vasodilation), so the surface reddens and warms; sweat pours from the eccrine glands and wets the surface; and the warm, humid air softens the outer horny layer, the stratum corneum, so that the skin briefly feels smooth and supple. Sweat both helps and taxes the skin: it hydrates the stratum corneum and carries urea and lactate, but a skin that stays damp for a long time loses some of its protective lipids and can become chapped or greasy according to its individual character. The transient abundance of blood near the surface is why the skin of a bather looks pink and feels warm without any tissue damage; the effects reverse within tens of minutes as the vessels return to their resting calibre.
The normal microbial flora of the skin also sees a busy session: sweat and warmth multiply the bacteria on the surface, and the benches, buckets and towels of a shared cabin are touched by many people. This is the hygienic reason for the classical rules of the sauna — rinse before entering, sit on a towel, shower after the session — which are developed under Sauna hygiene and facility cleaning. The practical benefits of the routine are real: less exchange of skin flora between bathers, less opportunity for the fungi and bacteria that cause rashes and skin infections in warm damp places, and quicker recovery of the skin's own balance.
Chronic skin conditions
The relation of bathing to the two common chronic skin conditions is treated in detail in Eczema and sauna and Psoriasis and sauna; the general point belongs here. For most people with eczema, the heat and sweating can itch and burn, and the sauna is best used cautiously with moisturising afterwards; for people with psoriasis, the regular wet-heat environment is tolerated by many and often enjoyed, with some reporting improvement of the plaques through the combined effect of moisture, loosening flakes and gentle scrubbing. In both cases the disease and its treatment remain the province of dermatology, and the sauna is a comfort, not a therapy.
Skincare around the session
The product side of the subject clusters around the session in the classic pattern: gentle cleaning before, nothing heavy during, and moisture after. Scrubbing with a loofah or scrub and salt-based exfoliants is traditional in several bath cultures, and it loosens the dead horny cells that the steam has softened — the custom belongs to the bath-visit routines of the facility, and its abrasiveness is a matter of taste and skin sensitivity. Moisturising cream applied after the shower and drying supports the stratum corneum whose lipids the session has drawn out; plain, unscented creams are safest for the situations discussed in the eczema article. What should stay out of the cabin are cosmetics: heavy make-up, perfumed body lotions and concentrated essential oils, which can be driven into the heated, vasodilated skin or evaporated into the shared air, and which increase rather than reduce the load on the skin's barrier.
Two further cautions belong in any skin article about heat. First, the heat-caused dryness of the face after many sessions is normal and reversible; it is not "skin ageing", and there is no evidence that sauna use accelerates skin ageing beyond the well-known effects of sunlight — for which the unwashed, shaved or scrubbed skin of the bather needs the ordinary sun protection in the summer days after bathing. Second, the skin over the whole body sits closer to the heat of the stove than any other part of the bather, which is the standing reason for the safety rules of distance and guard (see Burn prevention in a sauna and Sauna burns); nothing in the cosmetic routine alters that physics.
Summary
For most bathers the skin takes care of itself: heat, sweat and steam in moderation, washing around the session, a towel between skin and bench, and a little moisturiser afterwards. The skin-heavy traditions of the sauna — the soft towels, the scrubs, the rinsed wood of the cabin — are hygiene as much as luxury, and the encyclopaedia's skin-related pages stay close to that line: Skin temperature and Sweating cover the physiology, Sauna hygiene the practice, and the disease articles the special cases.
See also
References
- 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
- Baker LB. "Physiology of sweat gland function: the roles of sweating and sweat composition in human health." Temperature 6(3):211–259, 2019. doi:10.1080/23328940.2019.1632145
- 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