To examine one aspect of anti-inflammatory effect of carvacrol and its potential preventive effect in inflammatory disorders such as asthma, in the present study, the effect of carvacrol on IL-4 and increased IFN-γ and IFN-γ/IL-4 ratio as an index of Th1/Th2 activity on sensitized guinea pigs has been examined. This evidence concerns the gene IL4 and asthma.