It could be mange. I know mange is common among boxers and usually starts as little spots of missing hair. Tucker had mange as a 4-7 month old and sometimes it looked like he has bug bites under his hair...usually he would lose hair in those spots over the next few weeks. Most of the time dogs who lose hair due to mange lose it on their feet, head, shoulder blades and around their tail/bum. A vet can tell you if it is mange by doing a skin sample and then looking at it under the scope.
Good luck. Tucker ended up going on ivermectin everyday for 3 1/2 months but is all good now.