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If you were my co-worker and told me that the sound of chewing near you drives you crazy, I'd do my best not to eat at my desk or anywhere near you. Dang. That must suck for you.
If your current job environment doesn't allow you to keep sane either fight until it does, or find another that is more accomodating. Look into all of your ADA and FMLA options. Taking time off to care for yourself can be covered under the FMLA.
Replacing a good employee is very expensive for an employer. I would suspect (or at least hope) that yours will work with you to find a solution.