Histamin is a biogenic amine that acts as a signaling molecule in various physiological processes throughout the body. It is synthesized from the amino acid histidine through the action of the enzyme histidine decarboxylase. Histamin is involved in the immune response, acting as a mediator in allergic reactions, inflammation, and other immune-related activities.
In allergic reactions, histamin is released by mast cells and basophils upon exposure to allergens, such as pollen or certain food substances. It binds to specific receptors, primarily the H1 receptor, present on target cells in different tissues, leading to activation of specific cellular pathways. This activation results in symptoms commonly associated with allergies, including itching, swelling, hives, and increased mucus production. Antihistamines are commonly used to block the effects of histamin and alleviate these symptoms.
Histamin also plays a role in regulating stomach acid secretion and gastrointestinal motility. It acts on H2 receptors present on parietal cells in the stomach to stimulate acid production. Furthermore, histamin is involved in neurotransmission in the central nervous system, modulating sleep-wake cycles, appetite, and cognitive functions.
Excessive histamin release or impaired breakdown can lead to disorders like allergic rhinitis, asthma, urticaria (hives), and gastric hyperacidity. Histamin intolerance is a condition where individuals have a reduced ability to metabolize histamin properly, leading to various symptoms such as headaches, flushing, abdominal pain, and diarrhea. Management of histamin-related disorders involves allergen avoidance, medication with antihistamines or histamin receptor antagonists, and dietary modifications to limit histamin-rich foods.
