What the sauna is — and what it is not
A sauna is not a bath and it is not a swim. It is a warm, steamy box: the humidity does the work, softening retained shed on toes, tail tips and body until it loosens enough for the gecko to remove by rubbing and walking. Leopard geckos are the usual candidates, since they shed in pieces and commonly trap old skin around their toes, but the same setup suits other ground geckos with a stubborn patch. Think of it as recreating the humid hide at maximum strength, for a short, supervised session.
Setting up the box
Take a small plastic tub with a secure lid and ventilation holes. Line the base with paper towel soaked in lukewarm water, or pour in plain lukewarm water to a depth that reaches the gecko's belly and no higher — for most leopard geckos that is well under the chin, and the gecko must be able to stand with its head comfortably clear. The water should feel warm-neutral on the inside of your wrist, around the mid-80s Fahrenheit at most; if it feels hot to you, it is dangerous to a small gecko. Put the tub somewhere warm and draught-free, because the whole setup cools quickly.
Fifteen to twenty calm minutes, supervised
Lower the gecko in gently, lid on, and stay within sight for the whole session. Most geckos settle after a minute of exploratory walking; that walking is useful, since damp paper towel underfoot is already working on the toe shed. Fifteen to twenty minutes is enough — longer sessions chill as the water cools and add stress without adding benefit. Never leave a soaking gecko alone, and lift it out immediately if it is thrashing, gaping or trying desperately to climb the walls rather than settling.
Afterwards: help the shed, never pull it
The sauna's job ends with softened skin; removal is the gecko's job. Let it walk over a damp towel or its humid hide and rub. For skin that is visibly loose and flapping, you may roll a damp cotton swab gently across it to encourage an edge to lift, but the moment a piece resists, stop — pulling at attached shed tears the fresh skin beneath and is the classic way keepers turn a small problem into an open wound. Offer the sauna again the following day rather than forcing the issue in one session.
When stuck shed stops being a home job
Some presentations should skip the sauna and go straight to a vet: shed skin wrapped tightly around a toe that has swollen or changed color beyond the ring, shed retained over the eyes of a species with eyelids, or the same failure repeating shed after shed despite good humidity. Recurring stuck shed usually points to humidity, diet or health issues worth a professional look rather than an endless cycle of soaks. Logging each shed, each sauna and its result as dated duties in KinsLe's Care Teams gives you — and, if it comes to it, your vet — a clear record of how often this is happening instead of a vague feeling that it happens a lot.