One Sauna Session Briefly Boosts Immune Cells in Blood

A 30-minute sauna session with a mid-way cold shower temporarily increases all circulating white blood cell types, including neutrophils and lymphocytes, peaking during heat exposure and returning to baseline about 30 minutes after the session ends. The rise likely reflects mobilization of immune cells from tissues—a mechanism similar to exercise that could enhance immune surveillance—though cytokine changes were small and long-term effects remain unknown. The study involved 51 adults and was published in Temperature, focusing on immediate, not lasting, immune responses.