The Histamine in Stool test is designed to measure the level of histamine in the stool, which can indicate histamine intolerance or an IgE-mediated food allergy. Elevated histamine levels may result from impaired production of Diamine Oxidase (DAO), chronic inflammatory gastrointestinal conditions like celiac disease or Crohn's disease, food intolerances (IgG), or stress-related mast cell breakdown.