If you feel dizzy, lethargic or 'spaced out' this could be a temporary phase. If it persists for more than a few days, a health check would be wise. Sleep patterns and bowel habits may change. These will usually adjust themselves over a period of months.
If you were previously allergic or 'sensitized' to particular foods which are now being eliminated, you could feel withdrawal symptoms or even develop minor skin eruptions. Although usually self-limiting, if you are at all concerned a nutritional expert/health professional should be consulted.
Summary