I lost 15 pounds when I first got sick too and was really worried, but am back to normal now - 5 1/2 years later.
I didn't have the RAST test, I had an ELISA/ACT LRA test for 375 substances - chemical and foods - and discovered food and chemicals allergies that can cause a delayed reaction. Is the RAST test a blood test or skin scratch test? Does it say that it tests for immediate reactions only? There are cleanses that don't use herbs - just food or juices. Also, I did a metabolic analysis, adrenal function test, hepatic detox pathway function test, DMPS challenge to test for heavy metals, and had blood drawn to test ANA. I went through two years of dental work. I could only eat mashed up foods like oatmeal, veggie soup, bananas, avocadoes. What kind dental work did you have done? The metabolic analysis showed the a-ketoglutaric level at 127 and it should not be over 16. Other acid levels that were elevated were: Fumaric Pyruvic, Malic, and a-ketoadipic. Whatever all that means, who knows, but I was put on Niacinamide, which is vitamin B3, and also magnesium to see how that goes. One of the things I tested reactive to was Potassium Bromate - which is a process used in making some breads - it is also used in toothpaste, mouthwash, home hair weaves/perms, and some photo supplies. No wonder I have bad reactions to so many things! I am also reactive to Ethyl Acetate which is a food additive, but is also used as a lacquer solvent, and it is used in ice cream, beverages, candies, decaf tea and coffee! As far as chemicals: I tested reactive to halogenated Biocides, which is organochlorine compounds - in pesticides, solvents, hervicides, cleaning agents, and paint removers. Tested reactive to Carbamates, which are pesticides - some of these carbamates damage the cell membrane and can trigger chemical sensitivities. Tested reactive to Nitrosamine Mix.
So I understand about the losses we face with allergies and sensitivities. If you eat something or are exposed to something that you are reactive to, it may increase your allergic response for a period of a few days! And then what happens when you go to the store and they just sprayed for bugs, and then have to go get gas!?! Maybe I will also post this to the MCS forum.
The information I read says that the immune system may forget over a period of time - 3 - 6 months - of avoiding all the allergens, and you could try to re-introduce those foods after that amount of time, but I have not passed that mark yet.