Know where you're coming from there! It drives me mad.
Just a word of caution, as your tale sounds so like my journey with Kitty - the dairy allergy seems to have been the tip of a rather large iceberg. Of course, your experience may be (and hopefully will be!) different, but just so you're aware.
I've gone from thinking she's just allergic to dairy, to thinking it's dairy and wheat, to thinking it's dairy and wheat and avocados... Right now (and this is pre-allergy test results) the tally is: dairy, wheat, avocados, potatoes, chick peas, butter beans, cats... and that's without risking tomatoes, fish, nuts, oranges, strawberries etc (which I'm sure would be problems if I went there!)
I really hope your LO's skin continues to heal and that he does well on Neocate. It's such an upsetting condition to watch your lo struggle with. Kitty has always been very low on the charts and behind developmentally too, so don't feel bad if your lo is the same. I think they put a lot of energy into fighting illness when they suffer from bad eczema.
Best of luck and keep us posted. (Did the GP give you a spiral bound Neocate guide too? They're quite useful, as they give a few recipes to try when weaning, and also suggest stirring the Neocate into meals after cooking to add more nutrients and calories.)