Histamine dihydrochloride is primarily used in medical diagnostics and research. It is commonly employed in allergy testing to assess an individual's sensitivity to allergens. When administered in controlled amounts, it induces a histamine response, helping to determine the presence and severity of allergic reactions.

In addition, it is utilized in pharmacological studies to investigate the role of histamine in various physiological processes, such as immune response, gastric acid secretion, and neurotransmission. This compound serves as a reference standard in laboratory experiments to study histamine receptors and develop antihistamine drugs.

Furthermore, histamine dihydrochloride has applications in immunotherapy, where it is used to stimulate immune responses in certain cancer treatments, particularly in combination with interleukin-2 to enhance the effectiveness of therapy.