Histamine — पूरी मेडिकल गाइड (Hindi)
परिभाषा से लेकर पैथोफिजियोलॉजी, क्लिनिकल सिंड्रोम, डायग्नोस्टिक टेस्ट, एंटीहिस्टामिन/इमर्जेंसी ट्रीटमेंट और डायट/लाइफस्टाइल सलाह तक।
Contents — Jump to
Definition • Biosynthesis & Metabolism • Histamine Receptors (H1–H4) • Physiological Roles • Pathology & Clinical Syndromes • Investigations • Treatment & Drugs • High-Histamine Foods & Diet • Precautions & Pregnancy • FAQ
Definition — Histamine क्या है?
Histamine एक जैविक अमीन (biogenic amine) है — इम्यून और फिजियोलॉजिकल रिस्पॉन्स में महत्वपूर्ण mediator। यह मुख्यतः mast cells, basophils और कुछ न्यूरॉन्स (CNS) द्वारा स्टोर और रिलीज़ होता है। शरीर में histamine के प्रभाव कई रिसेप्टर टाइप (H1–H4) के माध्यम से होते हैं।
संक्षेप: histamine = allergy, vasodilation, gastric acid secretion और न्यूरोट्रांसमिशन में महत्वपूर्ण।
Biosynthesis & Metabolism (बायोसिन्थेसिस और टूटना)
सिंथेसिस
Histidine (एक अमीनो एसिड) से enzyme histidine decarboxylase (HDC) histamine बनाता है। यह प्रतिक्रया मुख्यतः mast cells, enterochromaffin-like cells (ECL) (stomach में) और कुछ neurons में होती है.
Storage & Release
Histamine granules के रूप में mast cells और basophils में स्टोर होता है। IgE-mediated allergen cross-linking, physical stimuli (trauma, heat), complement activation (C3a/C5a) और कुछ drugs (e.g., morphine) पर यह degranulate होकर extracellular compartment में रिलीज़ होता है।
Catabolism (टूटना)
- Diamine oxidase (DAO) — extracellular histamine का प्रमुख metabolic enzyme (intestinal, plasma)।
- Histamine N-methyltransferase (HNMT) — intracellular inactivation (especially CNS, liver) द्वारा N-methylation करता है।
DAO deficiency या DAO inhibitors वाले ड्रग्स histamine intolerance में श्रृंगारक होते हैं।
Histamine Receptors — H1, H2, H3, H4 (रिसेप्टर और उनका प्रभाव)
| Receptor | Location | Signaling & Major effects |
|---|---|---|
| H1 | Vascular endothelium, airway smooth muscle, sensory nerves, CNS | Gq → IP3/DAG → bronchoconstriction, vasodilation (capillary leakage), itching, wakefulness |
| H2 | Parietal cells (stomach), heart, vascular smooth muscle | Gs → ↑cAMP → gastric acid secretion, positive chronotropy/inotropy |
| H3 | CNS (presynaptic autoreceptors) | Gi → ↓neurotransmitter release (modulates histamine/acetylcholine/dopamine) — sleep/wake regulation |
| H4 | Bone marrow, immune cells (mast cells, eosinophils) | Chemotaxis, immune modulation — emerging role in pruritus & inflammation |
क्लिनिकली H1 और H2 को target करने वाले drugs सबसे उपयोगी रहें हैं; H3/H4 पर रिसर्च चल रही है।
Physiological Roles (शरीर में भूमिका)
- वेसलर इफेक्ट: Vasodilation, ↑vascular permeability → erythema, edema.
- ब्रोंकोकन्स्ट्रिक्शन: airway smooth muscle संवेदनशीलता बढ़ता है।
- गैस्ट्रिक एसिड: H2 → parietal cell acid secretion (peptic disease में clinical relevance)।
- सेंसेशन व पेन: sensory nerve stimulation → itching, pain modulation।
- स्लीप-वेक साइकल: CNS histamine wakefulness में योगदान देता है (H3 modulation)।
Pathology & Clinical Syndromes
Anaphylaxis (अनाफ़िलेक्सिस)
यह IgE-mediated severe systemic hypersensitivity है — rapid mast cell degranulation → massive histamine release → hypotension, bronchospasm, laryngeal edema, urticaria, GI symptoms। Emergency management में epinephrine life-saving है; histamine blockers supportive role निभाते हैं (H1 + H2)।
Urticaria / Angioedema
Wheal-and-flare reactions commonly mediated by histamine (H1) — antihistamines (H1 blockers) first-line therapy। Chronic spontaneous urticaria में higher doses या add-ons जरूरत पड़ते हैं।
Mast cell activation syndrome & Mastocytosis
Pathologic increase in mast cell number/activity → recurrent flushing, anaphylaxis, GI symptoms, bone pain. Serum tryptase elevated in systemic mastocytosis; KIT mutation (D816V) associated. Treatment: antihistamines, mast cell stabilizers, avoidance of triggers, cytoreductive therapy in severe cases.
Histamine Intolerance
DAO deficiency या excess dietary histamine → flushing, headache, hives, GI upset, tachycardia — diagnosis clinical + supportive testing (DAO activity, histamine levels) and response to low-histamine diet.
Peptic Ulcer & Acid-Related Disease
H2 receptor mediated acid secretion historically targeted by H2 blockers (ranitidine withdrawn in many markets; famotidine, nizatidine used) and now PPIs are mainstay.
Drug-induced histamine release
Certain drugs (morphine, vancomycin (red man syndrome), radiographic contrast, some muscle relaxants) cause non-IgE histamine release → flushing, hypotension — management: slow infusion, antihistamines, epinephrine if severe.
Investigations & Diagnostic Tests
- Serum tryptase (acute and baseline): elevated in systemic mast cell activation/anaphylaxis (sample within 1–4 hrs of event recommended).
- Plasma histamine — labile; timing sensitive; often impractical.
- DAO activity and urinary methylhistamine — in suspected histamine intolerance.
- Skin prick testing / specific IgE — for allergen identification.
- Complete blood count (eosinophilia), LFT/RFT as baseline before systemic therapy where relevant.
Clinical context और timing सबसे महत्वपूर्ण — e.g., anaphylaxis पे्रक्षण के तुरंत बाद tryptase भेजना उपयोगी है।
Treatment & Drugs (इलाज और दवाइयाँ)
Emergency (Anaphylaxis)
- Adrenaline (Epinephrine) IM 0.3–0.5 mg (adult) 1:1000 into lateral thigh — immediately; repeat q5–15 min as needed.
- High-flow O₂, airway control; IV fluids bolus for hypotension.
- Adjunctive: H1 antihistamine (e.g., chlorpheniramine IV) and H2 blocker (e.g., ranitidine or famotidine) — supportive, not a substitute for adrenaline.
- Bronchodilator (salbutamol nebulized) for bronchospasm.
- Consider IV corticosteroid (hydrocortisone/methylprednisolone) to reduce biphasic reaction risk (on specialist judgement).
H1 Antagonists — Classes & Examples
First-generation (sedating): chlorpheniramine, diphenhydramine — cross BBB, anticholinergic effects.
Second/third-generation (less sedating): cetirizine, levocetirizine, loratadine, desloratadine, fexofenadine — peripheral H1 blockade, less CNS penetration.
| Drug | Common adult dose | Notes |
|---|---|---|
| Cetirizine | 10 mg once daily | Some sedation in sensitive persons |
| Levocetirizine | 5 mg once daily | Active enantiomer of cetirizine |
| Fexofenadine | 120 mg once daily (or 180 mg) | Minimal sedation; good for driver/worker |
| Chlorpheniramine | 4 mg every 4–6 h (PRN) | Sedating; useful in acute relief |
H2 Blockers
Famotidine 20 mg BID — adjunct in severe urticaria/anaphylaxis (combined H1+H2 blockade offers better symptom relief in some cases).
Mast cell stabilizers & Others
- Cromoglycate (topical/nostril/eye drops) — prophylactic in allergic conjunctivitis/rhinitis.
- Ketotifen — H1 antagonist with mast cell stabilizing property (paediatric use in some countries).
- Leukotriene receptor antagonists (montelukast) — adjunct in allergic rhinitis/asthma and some urticaria.
- Omalizumab (anti-IgE monoclonal) — refractory chronic spontaneous urticaria/ severe asthma under specialist care.
Management of Histamine Intolerance
- Low-histamine diet (see section below).
- Avoid DAO-inhibiting drugs when possible.
- Consider supplemental diamine oxidase (DAO) in some markets — evidence mixed.
- Symptomatic antihistamines for pruritus/flushing.
किसी भी गंभीर allergic event में immediate emergency action (epinephrine) प्राथमिक है; antihistamines supportive हैं।
High-Histamine Foods & Dietary Advice (आहार)
कुछ खाद्य पदार्थ स्वयं histamine युक्त होते हैं या histamine-release/formation को बढ़ाते हैं। यदि histamine intolerance है तो निम्न पदार्थों से परहेज उपयोगी है:
Foods commonly high in histamine / promote histamine
- Aged cheese, processed/fermented cheeses
- Processed meats (salami, ham), smoked fish
- Fermented foods (sauerkraut, kimchi, soy sauce, vinegar)
- Alcoholic beverages (wine, beer)
- Some fish (tuna, mackerel) if not fresh — histamine formation (scombroid poisoning)
- Tomato, eggplant, spinach (variable)
Foods lower in histamine / recommended
- Fresh meat and fresh fish (properly stored)
- Fresh vegetables (except those listed above)
- Rice, gluten-free grains, fresh fruits (except citrus in some individuals)
- Plain yogurt (some tolerate) — but fermented foods vary by person
Diet response is individualized — elimination trial (2–4 weeks) under dietitian/clinician guidance advisable. For scombroid (histamine fish poisoning), supportive care and antihistamines help; prevention by proper refrigeration is key.
Precautions, Interactions & Special Populations
Drug Interactions
- Alcohol and CNS depressants add to sedation with first-gen antihistamines.
- CYP interactions: some antihistamines metabolized by CYP enzymes (e.g., loratadine) — check specific drug interactions.
- H2 blockers + H1 blockers used together for better symptomatic control in some acute settings.
Renal & Hepatic impairment
Some antihistamines (cetirizine, levocetirizine) require dose adjustment in renal impairment; hepatic impairment may alter metabolism for others. Check label and adjust.
Pregnancy & Breastfeeding
Certain second-generation antihistamines (loratadine, cetirizine) have reasonable safety data; use after risk–benefit discussion. First-generation sedating agents may cause neonatal sedation if used near delivery. Always consult obstetrician.
Clinical Pearls & Practical Points
- Anaphylaxis: adrenaline first — antihistamines are adjuncts and do not replace epinephrine.
- Chronic spontaneous urticaria: start with second-generation H1 antihistamine; if refractory → up-titrate dose (×2 or ×4 under guidance) or switch/add omalizumab.
- Red man syndrome with vancomycin is histamine-mediated — slow infusion and antihistamine prophylaxis useful.
- Scombroid poisoning presents like allergy after fish consumption — treat with antihistamines and supportive care.
- Histamine intolerance: consider DAO measurement, low-histamine diet and review medications that inhibit DAO.
Related Internal Links (आपके ब्लॉग के पेज)
- Heart Failure Diet — Complete Guide — fluid & sodium balance relevant when using diuretics that affect electrolytes.
- Biotin Deficiency — skin/nail changes differential with allergic dermatitis.
- Epistaxis (Nosebleed) — histamine/vasodilation can aggravate mucosal congestion.
- Onion (Allium cepa) — dietary phytochemicals that may modulate inflammation.
- Guava — Vitamin C — immune support; vitamin C may help some allergic symptoms.
- Banana — Potassium — supportive nutrition.
- Complete Medical Nutrition Guide — nutrition roles in immunity.
- Anjeer (Figs) — high-fibre, consider individual histamine tolerance.
इन internal links को अपनी साइट के पार्टिकुलर आर्टिकल URLs के साथ बदलकरयूज़र को और गहरा पढ़ने का अनुभव दें।
FAQ — अक्सर पूछे जाने वाले प्रश्न
Histamine allergy और histamine intolerance में फर्क क्या है?
Allergic reactions IgE-mediated immune response से होते हैं; histamine intolerance metabolic imbalance (DAO deficiency/excess intake) से होता है। दोनों में लक्षण overlap कर सकते हैं पर pathogenesis अलग है।
क्या antihistamines सब कुछ रोक सकती हैं?
Antihistamines H1-mediated symptoms (itch, sneeze, rhinorrhea, wheal) कम करते हैं; पर bronchospasm या hypotension जैसी life-threatening स्थितियों में adrenaline आवश्यक है।
क्या कुछ फूड्स histamine बढ़ाते हैं?
हां — aged cheese, processed meats, fermented foods, alcohol आदि histamine से समृद्ध होते हैं और intolerant व्यक्तियों में लक्षण उत्पन्न कर सकते हैं।
क्यों vancomycin से flushing होता है?
Vancomycin infusion तेज होने पर non-IgE mediated mast cell degranulation होता है (red-man syndrome) — slow infusion और antihistamine prophylaxis से रोका जा सकता है।
Key Takeaways — संक्षेप
- Histamine एक multifunctional mediator है — allergy, gastric acid, CNS roles।
- H1 blockers symptomatic relief देते हैं; H2 blockers gastric/adjunct roles में हैं।
- Anaphylaxis में adrenaline तुरंत दें; antihistamines supportive therapy हैं।
- Histamine intolerance management = low-histamine diet + avoid triggers; DAO role महत्वपूर्ण।