EDIT:....ugh, just realized this was 6 years ago too, but i'll keep what I posted up...lol.
Just something to throw out there as something to think about....
Maybe watch his eating patterns and how they contribute to any kind of frequent hormonal fluctuations. For example, most can attest to having their acne clear up when following a low carb diet, but right when they carb up, they break out. I think it is not so much staying high carb or low carb, but rather the fluctuations between the two. If he eats clean, then eats junk for a day or two, or even high carb/GI foods, then the fluctuations will be considerate imo to trigger a problem from my experiences.
When I go high protein and low carb or low carb CKD/Keto style, and whatever acne i get clears up. Then when I carb-up or refeed, that's when I run into problems.
I'm definately not an expert in this area for sure though.
I know doxy works well for a first try before stepping into Accutane. However, most may actually need the Accutane, but if they do, i'd go much lower doses than the usual prescribed amounts.
Definately make sure he is getting TONS of water!!! Very important.
Also, cut out any junk foods and fast foods as well. Whenever I eat a fast food meal, i'll get more problems......note: he may not even eat these foods at all though, but i'm sure you'd know that being his friend.
BMJ