So sad to read, must be hard at that age it is difficult anyway in your teens without this. Im in my twenties and inbetween jobs so am coping OK with the healing process as I can choose when to go out and can get plenty of rest etc. When I was at work with this it was horrible though, really really horrible but I just had to get through it.
ANYWAY here is the positive bit. I too got this from accutane and for the past few months have simply been leaving my lips alone as much as possible, leaving the skin and crusts in place where possible, eating fairly healthy, not smoking and cutting down on my drinking and exercising regularly and i am nearly healed!! I believe it is simply a process of allowing the layers of skin to grow back again!! If you believe the candida thing then it may be useful to order some probiotic tablets online for him to take as this helps even up the good and bad bacteria again after long courses of Antibiotics . I used them and theyve been good. I also had a colonic irrigation but for a young guy that may be hard to convince him to do!!
Tell him to look at it as a positive. Its a chance to just relax, exercise, eat healthy, chill out, listen music, read a bit and generally look after himself. Having a supportive mother like yourself is a huge positive he has. I wish my family understood but they just think im being a bit sensitive i think!!