From my experience, food sensitivities and intolerances can be far greater than just the digestive tract.
Gluten ataxia is just one example
“Our first aim in this study was to establish any therapeutic effects of the gluten-free diet in patients with gluten sensitivity presenting with ataxia. Our second aim was to provide further evidence, by studying patients with gluten ataxia but without enteropathy, that the nervous system can be the sole target organ of an immune mediated disease triggered and perpetuated by the ingestion of gluten.” http://jnnp.bmj.com/content/74/9/1221.full
