This is purely anecdotal on my part, but I am convinced that my daughter's
allergies contribute to her inability to concentrate.  She no longer has
any milk at all (unless she gets it accidentally), but I believe there may
be something else that she is allergic to that is contributing to her
sometimes acting like she is "in a fog."  I also have a close friend who is
an adult who said that when he had milk (before he knew he was allergic)
that he could not concentrate. Sounded almost like had similar symptoms to
diabetes--with wide mood swings, etc.

Good luck.