Can a wheat allergy or gluten sensitivity develop in adulthood or is it usually present from childhood? how is it diagnosed?

Yes /tests: You can be born with a genetic tendency to these issues, but they require life experience to develop & can do so at almost any age.Testing for tissue markers like transglutaminase IgA, and increased levels of IgG & IgA to wheat are considered likely indicators of the condition but must be done while the person is ingesting the material. Intestinal biopsy is the standard for labeling celiac disease