The influence of hardening procedures on immunological and leukocyte parameters in children aged 4–6 years

Aim. This study aimed to investigate the effects of hardening regimens on key immunolo­gical and leukocyte parameters in children aged 4–6 years in preschool settings. Materials and methods. Preschool children were allocated into three groups. The Hardening group (n = 53) underwent a regimen of cold temperature exposure five times per week. The Contrast group (n = 12) followed a similar hardening regimen (cold temperature exposure) but concluded each session with a sauna visit (+60 to +65°C, hot tempe­rature exposure). The Control group (n = 16) adhered to the standard kindergarten routine. Results. The hardening procedures did not induce significant alterations in immunoglobulin levels or leukocyte parameters. However, subtle changes in cytokine levels were observed in both the Hardening and Contrast groups compared to the Control. A positive correlation between TNF-α and neutrophils in the Control and Hardening groups suggested a baseline state of immune readiness. In the Contrast group, this relationship was inverted, showing a negative correlation, which indicates a modulation of the immune response following thermal stress. This altered state was further supported by a positive correlation between TNF-α and monocyte levels in the Contrast group. Conclusion. The absence of significant changes in leukocyte and immuno­globulin parameters, coupled with cytokine alterations that remained within normal limits, suggests that temperature exposure elicits an adequate immune response without evidence of pathological immune activation.