Does armpit hair or menstruation come first? There is no direct relationship between the development of armpit hair and menstruation, it depends on the individual’s body type. Some children will have their menstrual cycle and some will have their armpit hair first, but the two will have a mutually reinforcing effect. The development of axillary hair and pubic hair is a normal secondary sexual characteristic, and menstruation should occur at this time. In general, pubertal development begins after the age of nine, when the nucleus and breasts develop, followed by the development of axillary and pubic hair, and finally the first menstruation occurs. The sequence is usually breast development first, followed by the development of axillary and pubic hair, and finally the onset of menstruation. There is no certain relationship between axillary hair and menstruation. It is possible that axillary hair appears first and menstruation comes first.