Suggest Remedy To Clean And Prevent Blackheads In Children

I have recently noticed blackheads on my daughter 's sides of her nose (nostrils), she is turning 8 in one week. She has dry skin, so I've been using cetaphil on her face and body since she was born. she washes her face in the morning, and bath a night daily, then apply cetaphil and sunscreen on sunny days. How can I stop or clear this blackheads.? Are they caused by hormones or uncleaned pores ?
thank you,