Focus: Histamine signaling and pharmacologic management of allergic disease. Organized by drug class with clinical treatment references below.

• Brompheniramine
• Chlorpheniramine
• Diphenhydramine
• Hydroxyzine
• Promethazine
• Dimenhydrinate
• Meclizine

Second Generation Histamine-1 Antagonists

• Fexofenadine
• Loratadine
• Cetirizine
• Levocetirizine
• Desloratadine

• Cimetidine
• Famotidine
• Nizatidine
• Ranitidine (off market)

• Cromolyn Sodium
• Nedocromil (off market)

• Montelukast
• Zafirlukast
• Zileuton

Corticosteroids

• Fluticasone
• Mometasone
• Budesonide

• Prednisone
• Methylprednisolone

• Epinephrine

• Omalizumab
• Mepolizumab
• Reslizumab
• Benralizumab
• Dupilumab

Use this section when you’re starting from the patient presentation.

• Allergic Rhinitis → Treatment & Stepwise Therapy

(Intranasal steroid first-line; add antihistamine based on symptoms)

• Urticaria / Pruritus → Treatment Approach

(Scheduled 2nd-gen H1 blockers; escalate; chronic urticaria options)

• Angioedema → Histamine vs Bradykinin Angioedema

(Distinguish allergic vs ACEi/HAE)

• Anaphylaxis → Emergency Algorithm

(IM epinephrine first-line; adjuncts second)

• Asthma overlap / AERD → Allergic Asthma + Leukotrienes

Use this section when you’re starting from physiology/pathophysiology.

• Histamine Physiology (Synthesis, Storage, Release)
• Histamine Receptors (H1–H4) & G-Protein Signaling
• Type I Hypersensitivity (IgE → Mast Cell → Early/Late Phase)
• Hypersensitivity Types I–IV (Drug Rash Mapping)
• Eicosanoids, Leukotrienes, Prostaglandins (Inflammation Link)

• Quiz: Histamine & Antihistamines
• Case Bank (Rhinitis, Urticaria, Anaphylaxis)
• One-Page Algorithms (High Yield)
• Crossword Puzzle
• Crossword Answers

• Board pearl: 1st-gen H1 blockers cross the BBB → sedation + anticholinergic toxicity (esp. elderly).
• Clinical pearl: Angioedema without hives raises concern for bradykinin-mediated etiologies (ACEi/HAE).