We evaluated an anti-inflammatory enzyme drug Danzen (Serrapeptase: Takeda Chemical Industries, Ltd.) on 70 patients complaining of breast engorgement. These patients were randomly divided into 2 groups, a treatment group and a placebo group. A single observer, unaware of the group the patients were in, assessed the severity of each of the symptoms and signs of breast engorgement before treatment was commenced, and daily for 3 days, during which therapy was administered. Danzen was noted to be superior to placebo for improvement of breast pain, breast swelling and induration and while 85.7% of the patients receiving Danzen had "Moderate to Marked" improvement, only 60.0% of the patients receiving placebo had a similar degree of improvement. "Marked" improvement was found in 22.9% of the treatment group and 2.9% of the placebo group. These differences were statistically significant (P less than 0.05). No adverse reactions were reported with the use of Danzen. Danzen is a safe and effective method for the treatment of breast engorgement.