it really depends on your type of acne. if you only get a pimple here or there occasionally, then you might be able to get away with spot treating. but if you break out randomly everywhere, anytime, you're better off applying all over. that way you prevent them as well as treat existing ones.

Unless you have very mild acne, like 1-2 spots a week, it won't work. Spot treating never works for people who have anything more than the occasional whitehead. You have to apply BP all over to prevent future breakouts, also your skin tone might end up looking uneven if you have darker skin and if you spot treat only.