Erythromycin is a macrolide antibiotic used to treat acne and to help reduce the number of pimples. As a matter of fact, the exact mechanism by which erythromycin reduces lesions of acne vulgaris is not fully known: however, the effect appears to be due in part to the antibacterial activity of the drug. Bear in mind that the following adverse reactions have been reported occasionally: peeling, dryness, itching, and oiliness. Besides, irritation of the eyes and tenderness of the skin have also been reported with topical use of erythromycin. There are actually no adequate and well-controlled studies in pregnant women when it comes to the side effects of using this medication during pregnancy. However, Erythromycin should be used in pregnancy only if clearly needed. It is also not known whether this drug is excreted in human milk after topical application. However, it is excreted in human milk following oral erythromycin administration. Therefore, caution should be exercised when this medication is administered to nursing women.