HRH2 and duodenal ulcer: Histamine, a biogenic amine, plays a pivotal role in various physiological and pathophysiological processes, such as allergic and inflammatory reactions, gastric acid secretion, wake‐sleep disorders, and neurotransmission in the central nervous system.[15] The histamine receptor system comprises four members (H1R, H2R, H3R, and H4R), all of which belong to the Class A GPCR family.[16] Drugs targeting H1R, H2R, and H3R have been approved to treat allergic disorders,[17] gastroduodenal ulcers,[18] and narcolepsy,[19] respectively.