Interestingly, IgG is the longer-term response compared to the more immediate Immunoglobulin E response which causes the most dramatic allergy reactions such as rapid airway constriction.
The implication is that IgG type sensitivities are under-diagnosed because the symptoms are elusive and subtle, and ADHD often happens to be one of them.
"We recorded no difference in behavioural effects after challenge with high-IgG or low-IgG foods. These results suggest that use of IgG blood tests to identify which foods are triggering ADHD is not advisable. However, IgG blood tests might be useful in other diseases." [1]
To me, this says that any deviation from restricted diet caused a relapse in ADHD symtoms. A less technical explaination about IgG testing here: http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html
[1] http://marrym.web-log.nl/files/adhd-and-elimination-diet-rct...
I had somehow read only the part about the sequence of food reintroduction having no association but missed the conclusion from that, which now of course seems obvious.
That really is something different. I'm surprised that this lede was buried in the articles on this result I've read. So the mystery continues. Very curious.