Best acne treatment

Pimples started to appear again on my Daryl's face.  But he is not in need yet in need of the best acne treatment.  They are only pimples, not acne or the inflamed ones, where some even have cyst and nodules.

But I am not sure about those at his back.  Though they are only a few now, they are some that look like slightly bigger than a pimple, red and swollen.  Some are even achy.

I wonder if these acne or pimples can be caused by stress.  Lately, Daryl was so stressed up, he wanted to do every school work at one time.  He challenges his own self too much.  I have always told him to be cool and take things at a stride, to have fun once in a while, and not to pressure himself that much.  But oh, well, I know he knows what he's doing.  But I hope he'll have enough fun during the holidays.  Though there will be a lot to be stressed about the holidays, too,  I hope he can have a breather.