We analyzed the change of peripheral blood T cell subsets after moving into a house with a Healthy Air system (HAS) elimination system for various allergens, e.g. pollens, house dusts, etc. The 20 subjects were divided into an allergic group (13 subjects) and control group (7 subjects). We measured complete blood counts (CBC), white blood cell differentiation (DIFF), CD4/CD8 ratio, Th1/Th2 ratio, and percentage of CD4+CD25+T-cells and regulatory T-cells in peripheral blood, and these data were compared before and 3 and 6 months after moving into the HAS house. There was no significant difference in CBC, DIFF, CD4/CD8 ratio, and Th1/Th2 ratio before and after the move. The mean levels and 95% confidence interval of CD4+CD25+T-cells in the allergic group were as follows: before, 16.66% (12.99-20.34%); at 3 months, 13.86% (10.49-17.22%); and at 6 months, 12.66% (9.28-16.05%), respectively. Those in the control group were as follows: before, 13.60% (5.27-21.93%); at 3 months, 12.51%(5.41-19.61%); and at 6 months, 11.77% (3.93-19.61%), respectively. CD4+CD25+T-cells were significantly decreased at 6 months after the move compared to before the move in the allergic group (p < 0.01). However, there was no significant difference between before and after the move in the control group. The mean levels of regulatory T-cells were not different between before and after the move in both groups. The mean level of CD4+CD25+T-cells in subjects that had improved allergic condition was significantly decreased at 6 months after the move compared to before the move (p < 0.05). These results suggest that decreases in allergens in the home environment may affect lymphocyte subsets.