We didn't have it too bad, sensitive formula fixed most of our woes (post-boob milk).
Bloodwork came back on my son, all normal. Still working on getting in to see a shrink. Best luck we've had this last week keeping him home is ignoring the hitting as soon as he doesn't get his way or thinks he's in trouble for something, and moving him onto something else, usually physically disrupting it with hugs or tickles or something. Feels like reinforcing behavior to me, but it's that or the predictable 20-60 minutes of incoherent screaming we've had for months. There have been incidents where we tell him to not hit... and it feels like the attention drives it. Earlier he did it and we completely ignored it (wasn't hitting anyone, nor in danger of hurting himself) and he was over it in a few seconds. When he hits or something it presses my buttons, makes me want to go nuclear, throw him in his room and not let him out until he's gotten over it. Just low tolerance for that kind of thing. Instead mom has gotten him through it in a minute or so on more than one occasion and he's fine.
Too bad none of that will fly at school.
Part of what feeds this at home I think is we can't get him to nap like he does at school so in the evening's he's on a hair trigger since he's tired.