The present invention provides an antiallergic agent which ameliorates allergic diseases of infants, especially infants who have not yet birth, and has no side effects. The present invention relates to an antiallergic agent for infants including bifidus bacteria.本発明は、乳児、特に出生後間もない乳児のアレルギー性の疾患を改善し、副作用がない抗アレルギー剤を提供する。本発明は、ビフィズス菌を含む乳児向けの抗アレルギー剤に関する。