Another thought:
Are you using a gram scale to measure out the formula and water? Some kids are very sensitive to the concentration and the only way to make it exact is buy using a gram scale.
99.8% of kids (at least US ones) who need an elemental will tolerate at least one, either neocate or Ellecare. The 2 in 1000 who don’t generally have more going on than “just” allergies, so if he’s truly not tolerating any formula, you need to get the doctors to look deeper…
Also:
Alimentum Ready to Feed is different from the powdered version, I did hear of child handling the ready to feed better than the powdered version…
There is also “Nutramigen AA” I don’t know much about it, but I did hear of a kid that did better on this than either elemental formulas..
Also: going back to the hypoallergenic formula: kids can handle it better/worse PO (by mouth) vs. tube ((n)g or j)
Hope I didn’t overload you with too much info…