i found the answer to my question. I was reading a website on mercury detox. They had an excerpt from Andy Cutlers book about sulfer in the diet. I have lots of filings and it looks like the culprit. I just ate 2 grapefruits and it didn't cause that horrible reaction. There is a relation between parasites and mercury and there is some discussion on the website. What is also very helpful are the lists of sulfer and non sulfer foods. The website is livingnetwork.co.za. I know of a few dentists that could help me and plan to keep searching for information. Thanks to CZ.