A single 30-minute session in a Finnish sauna heated to approximately 163 degrees Fahrenheit or 73 degrees Celsius and paired with a brief cold shower midpoint produces a rapid, transient spike in circulating white blood cells.To discover this, researchers studied 51 adults with an average age of 50. The participants spent 30 minutes in the heated environment with a cooling break positioned precisely midway through the routine. Blood samples were collected immediately before the session, right after the session, and 30 minutes later to track real-time physiological shifts.Immediately after the heat exposure, researchers measured significant increases in several groups of immune cells, including neutrophils and lymphocytes. Neutrophils act as first responders that react quickly to infections. Lymphocytes include cells that produce antibodies, coordinate broader immune responses, and destroy infected cells.The researchers suggest that the session mobilized these cells from other areas of the body directly into the bloodstream, which is a temporary cellular redistribution that closely mirrors the effects of physical exercise. However, a higher concentration of immune cells in the blood does not automatically mean better protection against illness.The immune surge proved highly temporary, as neutrophil and lymphocyte counts returned entirely to their starting levels within 30 minutes of completing the session. While some other white blood cells remained elevated, the study did not test whether participants became better at fighting infections over time. Furthermore, because the routine included a cold shower, the experiment could not isolate the effects of heat stress alone.[Heinonen, I. H., Koivula, T., Hollmen, M., Immonen, J., Kunutsor, S. K., Jalkanen, S., and Laukkanen, J. A. (2026). Acute Finnish sauna heat exposure induces stronger immune cell than cytokine responses. Temperature, 1, 14. DOI: 10.1080/23328940.2026.2115572]Science and facts💡
![A single 30-minute session in a Finnish sauna heated to approximately 163 degrees Fahrenheit or 73 degrees Celsius and paired with a brief cold shower midpoint produces a rapid, transient spike in circulating white blood cells.To discover this, researchers studied 51 adults with an average age of 50. The participants spent 30 minutes in the heated environment with a cooling break positioned precisely midway through the routine. Blood samples were collected immediately before the session, right after the session, and 30 minutes later to track real-time physiological shifts.Immediately after the heat exposure, researchers measured significant increases in several groups of immune cells, including neutrophils and lymphocytes. Neutrophils act as first responders that react quickly to infections. Lymphocytes include cells that produce antibodies, coordinate broader immune responses, and destroy infected cells.The researchers suggest that the session mobilized these cells from other areas of the body directly into the bloodstream, which is a temporary cellular redistribution that closely mirrors the effects of physical exercise. However, a higher concentration of immune cells in the blood does not automatically mean better protection against illness.The immune surge proved highly temporary, as neutrophil and lymphocyte counts returned entirely to their starting levels within 30 minutes of completing the session. While some other white blood cells remained elevated, the study did not test whether participants became better at fighting infections over time. Furthermore, because the routine included a cold shower, the experiment could not isolate the effects of heat stress alone.[Heinonen, I. H., Koivula, T., Hollmen, M., Immonen, J., Kunutsor, S. K., Jalkanen, S., and Laukkanen, J. A. (2026). Acute Finnish sauna heat exposure induces stronger immune cell than cytokine responses. Temperature, 1, 14. DOI: 10.1080/23328940.2026.2115572]Science and facts💡](https://cdn4.telesco.pe/file/XGOWMOJE2kLrpGvcwnv9iVVb-tPNIofEzm55cC8-B9-AOM1Aj9-asf7r7IaqYjR7gvNnT_H2GvOKRQDwC526Vkh6KVPrOyvmtiO181peiy2il8HV3dkHaG7JxpSsEuuUKjNttKK7342iIqMT1cwSW6T8qWJgfiPiUYuLy5g2R04GlqyZALomLHZPiR2nJwfAETq1my_3QY_xCUrkxSXs6r-7_cvvyqe1p2ylVfjTozo8ci_SltcNdL4LRXOefV2ILXfFMW9kLrgFb33xB6AH4oNzhiQb5khlNxEMzHSumHv7bdmvNWtL0yjIsQ3xhZh-833yVJH2TbVEZW2WRuYqWA.jpg)
A single 30-minute session in a Finnish sauna heated to approximately 163 degrees Fahrenheit or 73 degrees Celsius and paired with a brief cold shower midpoint produces a rapid, transient spike in circulating white blood cells.To discover this, researchers studied 51 adults with an average age of 50. The participants spent 30 minutes in the heated environment with a cooling break positioned precisely midway through the routine. Blood samples were collected immediately before the session, right after the session, and 30 minutes later to track real-time physiological shifts.Immediately after the heat exposure, researchers measured significant increases in several groups of immune cells, including neutrophils and lymphocytes. Neutrophils act as first responders that react quickly to infections. Lymphocytes include cells that produce antibodies, coordinate broader immune responses, and destroy infected cells.The researchers suggest that the session mobilized these cells from other areas of the body directly into the bloodstream, which is a temporary cellular redistribution that closely mirrors the effects of physical exercise. However, a higher concentration of immune cells in the blood does not automatically mean better protection against illness.The immune surge proved highly temporary, as neutrophil and lymphocyte counts returned entirely to their starting levels within 30 minutes of completing the session. While some other white blood cells remained elevated, the study did not test whether participants became better at fighting infections over time. Furthermore, because the routine included a cold shower, the experiment could not isolate the effects of heat stress alone.[Heinonen, I. H., Koivula, T., Hollmen, M., Immonen, J., Kunutsor, S. K., Jalkanen, S., and Laukkanen, J. A. (2026). Acute Finnish sauna heat exposure induces stronger immune cell than cytokine responses. Temperature, 1, 14. DOI: 10.1080/23328940.2026.2115572]Science and facts💡
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