Histamine is often associated with seasonal allergies, but its role in the body goes far beyond sneezing and itchy eyes. This naturally occurring compound helps regulate immune responses, digestion, and even communication between nerve cells. For some people, however, the body may have difficulty breaking down histamine efficiently. When histamine builds up faster than it can be cleared, it may contribute to a collection of symptoms commonly referred to as histamine intolerance . Although this condition is still being studied and can be difficult to diagnose, understanding its potential signs may help you have a more informed conversation with your healthcare provider. What Is Histamine Intolerance? Histamine intolerance does not mean you're allergic to histamine itself. Instead, it generally refers to a situation where histamine accumulates because the body cannot break it down effectively. One reason may be reduced activity of an enzyme called diamine oxidase (DAO) , whi...