Histamine accumulation syndrome is sometimes improperly referred to as “histamine intolerance.” Although this term is commonly used, it’s important to understand that it does not represent an intolerance in the classic sense (such as lactose intolerance, which is linked to a well-defined enzymatic deficiency, or gluten intolerance—both of which can be diagnosed with specific tests). So, let’s take a closer look at what it actually is.