I have had indigestion and gastric issues for a long long time, almost since childhood. Mostly constipation. Recently i have seen some random skin allergies where my skin develops red rashes which itch and then vanish in 10 15 minutes. I guess i am having some allergies/intolerance. But i am unable to figure out what tests i need to get done since both the symptoms very different from each other. Could be gluten, lactose (common things i have been hearing about) or anything else. Need suggestion on which tests i need to get done? Food allergy? Food intolerance? Or anything else that exists?