Food Intolerances and Sensitivities

I remembered that Michael Moore once wrote:

Normally, poor gastric secretions result in extended presence in the stomach of undigested food, allowing an allergic person to acquire food sensitivities, thereby worsening systemic reactions such as dermatitis.

It always resonated with me that canker or ama would lead to these kind of things. But how to be sure about this? I'm not sure how to search the literature for this.