I wouldn’t at that age unless she smells. and even then I would use apple cider vinegar and coconut oil. I would wait till puberty age

My son came from playing outside one days arms on 10 he’s 3 my mom just told me put him in the tub a good washing problem went away if I used deodorant he would have to continue wearing it but gag is when I was a vegetarian I NEVER wore deodorant arms never stunk even after working out so I get it

hey boo! if her smell is an issue try a gentle natural deodorant that works super well and won’t upset her nervous system, endocrine system, sweat glands, or immune system! try dr squatch in the scent fresh falls it’s very gender neutral clean smelling. if you want something gentler but that works less well lume is an option.