Symptoms of Precocious Puberty
In girls, the telltale signs of precocious puberty include any of the following before 7 or 8 years of age:

breast development
pubic or underarm hair development
rapid height growth - a growth "spurt"
start of menstruation (her period)
acne
"mature" body odor

In boys, the signs of precocious puberty before 9 years of age include:
enlargement of the testicles or penis
pubic, underarm, or facial hair development
rapid height growth - a growth "spurt"
voice deepening
acne
"mature" body odor

Many kids who show some of the early signs of puberty have what's known as "partial" precocious puberty. Some girls, usually beginning between the ages of 6 months and 3 years, may show breast development that later disappears or may last without other physical changes of puberty.

Similarly, some girls and boys may have early growth of pubic and/or underarm hair that isn't related to other changes in sexual development.

Kids with "partial" precocious puberty may need to see their doctor to rule out "true" precocious puberty or other health problems. But most need no treatment and usually will show the other expected signs of puberty at the usual age.