Abstract An oil of Minthostachys verticillata (Griseb.) Epling was analyzed by GC. The main constituents identified were pulegone (63.0%) and menthone (16.4%). It was found that the oil inhibited Î²-hexosaminidase release from basophils. Forty-two percent of the cells present in lymphocyte cultures stimulated by the oil were CD8(+) T cells and showed higher IFN-Î³ levels than non-stimulated cultures (p < 0.05). According to these results, the oil was considered to be a Th1 deviation inducer, inhibiting the immediate-type allergic reaction.