A lot of sweaty hair on the arms of a 9-year-old boy is usually normal.
Puberty usually begins around the age of 10, and a few boys may have earlier puberty and may begin to develop secondary sexual characteristics at the age of 9, which manifests itself in the enlargement of the male penis and testicles, increase in body hair and armpit hair, protruding laryngeal knots, low voice, muscularity, and the appearance of whiskers on the lips, and so on. So it is usually normal for a 9-year-old boy to have a lot of sweaty hair on his arms.
Puberty is the second peak of growth and development in a person’s life, this time the body is in a stage of rapid growth and development, so signs will appear a series of changes, parents do not have to be too nervous, if the child is not accompanied by other discomforts, generally do not need to worry too much.
If a 9-year-old boy has a lot of sweaty arms and other discomforts, it is recommended to consult a doctor for standardized treatment under the guidance of the doctor.