Nα-Methylhistamine dihydrochloride serves as a key metabolite marker for histamine activity in biological systems, particularly in research on allergic responses and mast cell activation. It is quantified in urine or plasma to evaluate histamine turnover, supporting the diagnosis of conditions such as mastocytosis and chronic urticaria. Additionally, as a selective agonist for the H3 histamine receptor, it is utilized in pharmacological studies to explore central nervous system functions including sleep regulation, learning, and memory. It also facilitates investigations into the modulation of other neurotransmitter release in animal models, contributing to drug development for neurological disorders like Alzheimer's disease, ADHD, and circadian rhythm disruptions such as jet lag. Furthermore, it aids in understanding histamine metabolism and the impacts of antihistamines or histamine-modulating therapies.