13/05/2026
Histamine is not only involved in allergies; it also acts as a neurotransmitter in the brain that regulates alertness, attention, sleep-wake cycles, motivation, and cognitive processing. Researchers are investigating whether excessive histamine activity or impaired histamine breakdown may contribute to symptoms that overlap with ADHD, including hyperactivity, poor concentration, executive dysfunction, irritability, insomnia, and “brain fog.” DAO is the primary enzyme responsible for breaking down dietary histamine in the gut, and reduced DAO activity can lead to histamine accumulation, a condition referred to as histamine intolerance (HIT).
A 2024 paper titled “Prevalence and Clinical Picture of Diamine Oxidase Gene Variants Associated with Diamine Oxidase Deficiency in ADHD Children and Adolescents” published in the National Institutes of Health repository reported that a high percentage of children with ADHD carried AOC1 gene variants linked to lower DAO activity. Another study, “Interaction of Diamine Oxidase with Psychostimulant Drugs for Attention-Deficit/Hyperactivity Disorder Treatment,” published by MDPI, explored how ADHD medications interact with DAO metabolism. Researchers such as Hilario Blasco-Fontecilla have also proposed that histamine may partly explain the known overlap between ADHD and allergic or atopic conditions like asthma, eczema, rhinitis, migraines, gut inflammation, and sleep disorders. However, scientists emphasize that this is currently a correlation and hypothesis-driven research area — not proof that histamine intolerance causes ADHD. Low-histamine diets or DAO supplements may help some individuals who have both ADHD symptoms and clear histamine-related issues, but these approaches are considered complementary and should not replace evidence-based ADHD treatment.