Syphilis is a common infectious disease caused by the syphilis spirochete, with tertiary syphilis being the most severe and most infectious stage. Therefore, breastfeeding is not allowed if one has tertiary syphilis, as breastfeeding is one of the transmission routes of syphilis. If breastfeeding occurs, syphilis can potentially be transmitted to the child through the breast milk. The breast milk of syphilis patients contains syphilis spirochetes, and if a syphilis patient breastfeeds a child, it essentially means transmitting this pathogen to the newborn through the milk. Thus, syphilis patients are prohibited from breastfeeding.