Many White Pimples on my Back. Please Show Me How to Treat Them? (photo)

I'm 22 years old. I have had many white pimples on my back for 7 years. They are not itchy or painful, just make my back look rough and not nice. Sometimes I rub them and then they are going to be red. After few days, they are white again.I'm using the Eclaran 5 cream, but they are still on my back. Could you please tell me what those white pimples are and how to treat them ? Thank you so much!