How do I know I have food allergy I had no allergy in the past I have just ibs and stomach cramps its possible to devolpe allergy later in life?

Yes. Most adult food allergies are to nuts and sea foods. In my experience running a panel for food allergy is misleading at best when it comes to IBS unless you have a specific food that reliably causes symptoms every time. It is possible to develop lactose intolerance and gluten sensitivity. I have included info regarding these. Best of luck.