I'll be fascinated to see how this plays out for people with autoimmune conditions - generalised heightening of the immune system feels like it would be dangerous for those people. Are any immunologists lurking who might be able to speculate?
It seems like it could also be quite dangerous for those with food allergies.
Its often completely normal to use healthy controls in a trial like this, healthy people not getting ill is your target audience and the long term stage 3 will be against healthy people. So many drugs are not tested against obvious groups that might produce a poor result to make the findings as strong as possible but it means in a lot of cases chronically ill people are making judgements on no data at all.