Can a 15 year old get Botox injections for under arm sweating?

Yes, with the consent from a legal guardian an adolescent can receive Botox for excessive sweating. Discuss your options with a board certified plastic surgeon or dermatologist. Best, 

Botox can actually give excellent results when used to treat excessive sweating of the underarms, palms, and soles of the feet. I have seen results last anywhere from 6 months to 1 year! For 15 year olds, parental consent is required for the procedure, but it is otherwise safe. Hope this helps!