Cold exposure triggers an immune response as the body perceives a threat of death, activating immune modulators.

“Keep in mind that one of the variables that's been measured quite a lot in laboratory studies of deliberate cold exposure is the increase in immune system markers. So I'll provide a few links to some of these studies. Although, nowadays there are many, many of them. But it's very clear that deliberate cold exposure can increase the release and the production of different immune molecules and immune cells.”