An immunomodulator is provided which is capable of oral intake for improvement, treatment and prevention of human immunological diseases and which is used to treat, improve and prevent human immunological diseases, especially, autoimmune diseases and allergic diseases such as hepatic cirrhosis, hepatitis, diabetes, inflammatory bowel diseases, chronic rheumatoid arthritis, asthma and cutaneous atopy, allergic diseases and cancers by a new method that can control the redox state of macrophages or monocytes, and can be incorporated into a drug, a food, a nutrient, and an infusion. The contents of oxidative glutathione and reductive glutathione in macrophages are monitored, and the ratio of oxidative glutathione and reductive glutathione is examined, whereby macrophages are classified into oxidative macrophages and reductive macrophages having different functions. The degree of progression of various autoimmune diseases is analyzed from this standpoint. On the basis of the results, an immunomodulator capable of oral intake which contains a substance having an activity of changing a content of reductive glutathione in macrophages to solve the above-mentioned problem and which is intended to treat, improve and prevent human immune diseases is provided.