Read the article I just put up on mucousal immunity and th1/th2 imbalance. A person with such sensitivities typically has a th2 dominant immune system. Study the hell out of it. Other things can cause it, but thats the best place to start. Also look into boosting t suppressor cells. And do whatever you can to give your immune system a break. And look up leaky gut if you tie your reactions to any foods. Immune system therapy should be your main focus though.
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