A new study from Finland has found that a single sauna session can temporarily increase the number of white blood cells circulating in the bloodstream. These cells play an important role in the body’s defence system, helping identify and respond to infections and other potential threats.
The findings offer fresh insight into how exposure to heat may affect immune activity. However, researchers caution that a short-term change in immune cells does not necessarily mean a person will have stronger long-term protection against illness.
Study Examines 51 Adults
Researchers studied 51 adults, with an average age of around 50, during a 30-minute Finnish sauna session. The routine included a brief, two-minute shower after the first 15 minutes.
Blood samples were collected before the session, immediately afterwards and again 30 minutes later. The researchers measured white blood cells and several chemical messengers involved in immune responses.
White Blood Cell Levels Rose Temporarily
The results showed increases in the circulating levels of all the white blood cell groups measured. Two important types, neutrophils and lymphocytes, rose immediately after the session but returned to their initial levels within approximately 30 minutes.
Neutrophils are among the immune system’s early responders to infection, while lymphocytes help recognise specific threats and coordinate immune responses.
Researchers also measured 37 cytokines, which are proteins that help immune cells communicate. Only two showed significant overall changes, suggesting that the immediate response involved immune-cell movement more clearly than widespread changes in these signalling molecules.
