Nine-week-old boy last year found to have armpit odor, this year found a few armpit hairs, consider it a normal phenomenon, because boys after the age of 9, there can be varying degrees of development of secondary sexual characteristics, such as the growth of armpit hair. Armpit odor generally refers to fox odor, the occurrence of fox odor and heredity has a certain relationship, in addition to a large number of sports as well as hot weather can also aggravate the armpit odor, this and the child’s age is not necessarily related, and is not a phenomenon that occurs only after the boy enters puberty. The current medical definition of precocious puberty is that boys have the development of secondary sexual characteristics before the age of 9, such as testicular enlargement, low voice, long beard, etc., because the child is now 9 years old, and only a small amount of armpit hair appears, consider it normal. It is recommended that the patient should consult the doctor in time if there is any discomfort, and should not be negligent so as not to delay the condition.