I wanted to comment on this thread because of our experiences over the last
year with food and behavior.
I have two daughters.  One (5yo) has allergies to peanut, egg and milk.
 Classic reactions and diagnosis.

The other (9yo), we always believed to be allergy free.  She had numerous
ear infections, complained often of being tired and became constipated if
she had too much milk.  Although seeming to be very bright from a young
age, she had trouble making friends, controlling her emotions and paying
attention. She could not follow through with anything.  We'd send her to
her room to get dressed, find her there an hour later staring at a sock.
 She also developed over time a tendency to laugh hysterically for no
reason, and to shout repetitive nonsense phrases.  The behavior came in
waves - sometimes she was a sweet normal kid, sometimes she completely
could not cope.  She was given a diagnosis of ADD with "probably a lot more
going on."    At about the same time, we noticed a correlation between
these behavior patterns and milk consumption.  We stopped milk, and it
helped her a lot.  The really weird stuff stopped, and a persistent skin
condition started to clear up - but she remained spacey and became more
hyperactive.

During this time the school evaluated her for SPED, because she couldn't
get *any* work done in class (or at home for that matter...)  Usually we
saw blank worksheets sent home.  We also started to eliminate corn and
wheat from her diet.  It turns out that wheat is ok for her, but the
changes with pulling corn were incredible.  It's as if this intelligent,
driven, mature, outgoing kid suddenly woke from a stupor.  She does all her
work at school - and gets the answers right :-> -  homework is finished
before getting home, interested in sports, making new friends - wow.
  People who haven't seen her for a while notice the change immediately.
  Of course, she's not perfect. Still picks on her little sister, doesn't
want to clean the disaster area we call her room, etc. - but at least she
has the tools to deal with things like everyone else now.

Sorry for such a long post - but this has really changed her life.  There's
a high correlation of kids with ADD and allergies in the same families.  A
lot of people doubt that food can cause behaviors that look a lot like ADD.
 Our pediatrician worked with us, and has seen similar stories with
different foods.  Does anyone know if studies have been done? - at this
point it seems that all the evidence is anecdotal.

Thanks for listening.

Lisa