I guess it really depends how the trainer organize his classes. In my case, my trainer is a former European champion, he knows the potential danger and he really cares about us. We use head protection, he pairs us wisely to avoid accidental injuries, sparring is optional, and 75% of our time is shadow boxing, heavy bag training and padding. So, we end up doing 3-4 rounds of sparring per week. I may get a couple of soft jabs in my head.
Like so many things, it's wise to evaluate the people who are teaching and the methods that they use. I toyed with the idea, but I decided against it because of my shoulders.
