The present invention discloses a pharmaceutical composition for inhibiting increase of immunoglobulin A (IgA) comprising β-glucan and a pharmaceutical acceptable carrier. The β-glucan is extracted from Saccharomyces Cerevisiae, and the effective dose of the β-glucan is 300-450 mg/70 kg of body weights/per day, preferably, 350-400 mg/70 kg of body weights/day.
