Dictionary Definition:
Adjective.
: excessively or abnormally sensitive: abnormally susceptible physiologically to a specific agent (such as a drug or antigen)~ Merriam-Webster
Elizabeth's take on this term...
A hypersensitive person may experience reactions to chemicals, pharmaceuticals, foods, or other substances that do not have an adverse effect on non-hypersensitive people. According to my Trigger Theory of Multiple Sclerosis, every person who suffers from a chronic autoimmune condition is hypersensitive.
A synonym to autoimmune. Abnormally sensitive to external triggers of inflammation.
A hypersensitive person may find that seemingly innocuous foods, like lettuce or potatoes, causes them to experience a flare in inflammation and new or more intense symptoms.