When do children begin to sweat and have BO?
If you look at a classroom of fourth-grade children or eighth-grade children, you will quickly notice that children develop at very different rates. The differences depend partly on genetics and partly on the environment (obesity, for instance, sometimes triggers earlier puberty).
Girls typically begin to have underarm odor and perspiration anytime after their eighth birthday and boys anytime after they turn 9. If these changes happen earlier, or haven't happened by 13 in girls or 13 1/2 in boys, it's wise to check with their pediatrician to be sure that everything is on track.