I have to say it sounds an awful lot like he has a food allergy, intolerance or sensitivity. This could also be the underlying cause for his other illnesses. Our immune systems are based primarily out of our gastrointestinal tract. When we eat a food our bodies do not agree with, our bodies either trigger a direct immune response to the food or an indirect immune response. This will determine the severity of the reaction and can sometimes be a reason for a delayed reaction by up to 72 hours. Either way, the immune system becomes overloaded, especially if the problem food is continually consumed. Over time this can lead to auto immune disorders and compromised function of systems. The kidneys are one of our bodies detoxifying organs, as this is how we get rid of waste. The liver is another key detoxifier. You mentioned he has a kidney disease so it does fit the scenario.

I'd suggest getting a food allergy test and a food sensitivity blood test (yes they are different tests). I think the food sensitivity blood test will be where you find your answer though, since food allergies are usually apparent immediately after the irritant is consumed. Usually the sensitivity tests are available through homeopathic doctors, which are usually listed as chiropractors in their listings (phonebook or internet). Please let me know if you have any questions. I've recently gone through the experience of learning about food reactions and have been on a recovery plan. Good luck.