Not once you have one: the MJA randomized trial of 157 people with fresh colds found sauna sessions did not significantly reduce overall symptom severity - inhaling hot air has no significant impact on the common cold.
The prevention question is separate and unsettled: one small study found regular sauna-goers reported about half as many colds over six months, but confounders limit it. When sick, 80-degree heat adds dehydration risk, not recovery. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper .
What to do
Common questions
Does sauna help a cold?
Not once you already have it - the one good randomized trial tested exactly this and came back negative. The Medical Journal of Australia trial randomized 157 people with fresh colds to sauna sessions or control and found no significant difference in overall symptom severity over the following days - their conclusion is flat: inhaling hot air in a sauna has no significant impact on the common cold. There were crumbs (slightly lower symptom scores on day 2, less medication use on day 1), but the headline result is no. The prevention question is separate and genuinely unsettled: a small Austrian study found regular sauna-goers reported about half as many colds over six months as non-users - but that is one small study with confounders (sauna-goers differ from non-sauna-goers in lots of ways), not a verdict. What is clear: once infected, the sauna does not shorten or soften the course, so sweating one out is not a strategy - and dragging a feverish, dehydrated body into 80-degree heat adds risk, not recovery. Sauna for relaxation when well; rest, fluids, and comfort measures when sick.