Immune balance adjustment agent

Provided is a novel immune balance adjustment agent for adjusting the immune balance of an organism. This immune balance adjustment agent is one which: contains a euglena-derived substance; and adjusts the Th1/Th2/Th17 immune balance, which is the balance of immune responses derived from Th1, Th2 and Th17 in the organism. The immune balance adjustment agent is used to improve physical constitutions in which the Th1/Th2/Th17 immune balance leans toward Th2, and in the prevention or treatment of diseases to which a lean toward Th2 in the Th1/Th2/Th17 immune balance contributes, by adjusting the Th1/Th2/Th17 immune balance in a manner such that the immune response derived from Th1 is adjusted in a relatively superior direction relative to the immune responses derived from Th2 or Th17. This agent is to be administered prior to the period during which the onset of a disease to which a lean toward Th2 in the Th1/Th2/Th17 immune balance contributes is predicted.