What age is undamaging to stay using deodorant underneath the arms?

my 9 year old get me to have a see of her underarms the other day.and i be surprised to smell a slight flavour of BO...is this normal?i thought kids didnt smell till much elder .like 14-16..im not sure how undamaging the usual adult sprays are.is near something else she can use? theres no exact age just as soon as you inaugurate to sweat i suppose - she'll be fine to use a deodrant just put together it a roll on as the sprays are more harmful, you don't want her getting bullied at conservatory for smelling kids can be cruel!!
there's teen deodrant. She must be starting puberty early. I don't meditate deodrant will harm her... I am 13 and have B.O. for over a year.