Histamine is an organic compound (a biogenic amine) made from the amino acid histidine.
- It acts as a signaling molecule (neurotransmitter + immune mediator).
- Stored mainly in mast cells and basophils (types of immune cells).
- Released during immune responses, injury, or allergic reactions.
🔬 Explanation (What Histamine Does)
Histamine has multiple roles in the body:
1. Immune System / Allergic Reactions
- When the immune system detects an allergen or injury, mast cells release histamine.
- Histamine causes blood vessels to dilate and become “leaky,” allowing immune cells to reach the site.
- This leads to redness, swelling, itching, and hives.
2. Stomach Function
- Histamine is released in the stomach lining.
- It stimulates parietal cells to secrete gastric acid (HCl), which is essential for digestion.
3. Brain / Nervous System
- Acts as a neurotransmitter in the brain.
- Helps regulate wakefulness, appetite, and cognition.
4. Blood Vessels & Smooth Muscle
- Causes vasodilation (widening of blood vessels).
- Can trigger smooth muscle contraction (e.g., in airways → wheezing/asthma).
📋 Conditions Linked to Histamine
- Allergic reactions (hay fever, hives, anaphylaxis).
- Asthma (airway constriction).
- Peptic ulcers / acid reflux (too much histamine → excess stomach acid).
- Histamine intolerance (trouble breaking it down → headaches, flushing, gut issues).
💊 Medications That Target Histamine
- Antihistamines (H1 blockers) → for allergies (diphenhydramine, loratadine).
- H2 blockers → for stomach acid (ranitidine, famotidine).
- Mast cell stabilizers → prevent histamine release.
👉 In short:
Histamine is a natural chemical messenger involved in immune defense, stomach acid production, and brain signaling. Too much histamine release causes allergy symptoms, while controlled release is essential for normal body functions.