The redness of the perineum of a baby girl may be caused by the lack of timely cleaning after defecation or friction caused by tight clothing. It is important for girls to take care of their perineum, wash it with warm water every day, ensure that the area is clean and dry and well ventilated, and try not to use diapers, otherwise the problem of infantile vaginitis is likely to occur. Now you can consider applying zinc oxide ointment or erythromycin ointment to treat the situation on the basis of cleanliness. It is best to stop wearing diapers for the time being.