It is normal for a nine-year-old daughter to have a breast nucleus on one side of her body. Girls usually nine to twelve years old around the secondary sexual characteristics gradually began to develop, if the usual nutrition is rich or by genetic factors or living environment and other factors, there may be the development of the breast nucleus, is a normal physiological phenomenon, with the age of the growing, the development of the breast nucleus will gradually increase the phenomenon. In the diet should be nutritionally balanced and comprehensive, pay attention to do not eat spicy and stimulating food, appropriate exercise, pay attention to the breast area of cleanliness and hygiene. If the development of breast nucleus is fast, consult a doctor in time to exclude disease factors. If you need to use medication, it is recommended to standardize the use of medication under the guidance of a doctor, scientific treatment.