Or is it just me? If I’m in a cold place for a while, I have an increased tendency to sweat under my arms. My understanding is that sweat is a heat-reducing mechanism, so this seems counter-intuitive. (Although perhaps underarm sweat is of a different nature to begin with.)
It may be Hyperhidrosis. It typically happens in the underarms, palms of the hands, and soles of the feet. It’s from overactive sweat glands and can happen in a variety of situations that have nothing to do with being hot. It can be treated with prescribed ointments. For longer lasting relief, botox injections can be used to block the nerve signals that would lead to sweating.
Could be you are sweating just as much as usual but in the cold it is more noticeable because it feels cold and it also stays more because it doesn’t evaporate as easily.
That sounds likely. Even in a cold place the underarms can stay quite warm as does the rest of your body internally and the temperature still has to be regulated.
While sweating’s main cause involves one’s thermal regulatory mechanism for cooling, that’s far from the only reason it happens. Caffeine, nicotine, alcohol, and many other drugs and medications will cause a sweating response. Capsaicin (the ‘heat’ in hot peppers) also triggers it. Many disease states such as heart failure, thyroid derangement, abnormally high or low blood sugars, and so on can trigger it. Hormone fluctuations are a big reason for it.