Mast cell concern, normal blood wk, but flushing, short term rashes, sensitive skin, gi issues, allergies, allergy test change from all pos. to all neg.?

See a specialist: Normal blood work taken when you are feeling relatively "normal" may not exclude all cases of mast cell disease. It may help to recheck certain labs (e.g., tryptase) within a couple hours of the start of an episode. There are also other potential causes for your symptoms, such as certain tumors, dermatographism, etc. I would see an expert in mast cell disorders and/or flushing disorders for help.