What is the most appropriate antihistamine for symptomatic relief of a sore throat caused by allergy or post‑nasal drip in an adult?

Antihistamines Are Not Appropriate for Throat Infections

Antihistamines do not treat throat infections and should not be prescribed for this indication. If your sore throat is caused by post-nasal drip from allergies, a second-generation antihistamine like fexofenadine or loratadine is appropriate; however, if you have an actual throat infection (bacterial pharyngitis), you need antibiotics, not antihistamines.

Understanding the Question: Infection vs. Allergy

The term "throat infection" typically refers to bacterial or viral pharyngitis, which antihistamines do not treat. However, if you are experiencing throat irritation from post-nasal drip due to allergic rhinitis, antihistamines can help by reducing the nasal secretions that drip down and irritate your throat. 1

For Allergic Post-Nasal Drip Causing Throat Irritation

First-Line: Second-Generation Antihistamines

Fexofenadine is the preferred choice because it provides complete non-sedation even at higher doses, making it the safest option for daytime use without performance impairment. 1, 2

• Fexofenadine 120-180 mg once daily is the gold standard when sedation must be absolutely avoided (driving, operating machinery, work requiring alertness). 1
• Loratadine 10 mg once daily is an acceptable alternative that is non-sedating at recommended doses and typically less expensive. 1
• Desloratadine 5 mg once daily offers superior decongestant and anti-inflammatory effects compared to loratadine, which may benefit patients with significant nasal congestion. 1

Avoid These Options

• Cetirizine causes mild drowsiness in 13.7% of patients and can impair performance even when patients don't feel drowsy, so it should be reserved for cases where other antihistamines have failed. 1, 3
• First-generation antihistamines (diphenhydramine, chlorpheniramine) cause significant sedation, anticholinergic effects, and performance impairment and should be avoided for simple allergic rhinitis. 1

Important Limitation

Oral antihistamines effectively reduce rhinorrhea, sneezing, and itching but have limited effect on nasal congestion. 1 If congestion is prominent, add an intranasal corticosteroid (such as fluticasone) rather than switching antihistamines, as intranasal steroids are more effective for controlling the full spectrum of allergic rhinitis symptoms. 1

For Upper Airway Cough Syndrome (Post-Nasal Drip with Cough)

If your throat irritation is accompanied by chronic cough from post-nasal drip lasting more than 8 weeks, the treatment approach changes completely:

First-generation antihistamines combined with a decongestant become the evidence-based standard. 4, 5

• Brompheniramine 12 mg + pseudoephedrine 120 mg (sustained-release) twice daily is the preferred regimen based on randomized controlled trials. 4, 5
• Alternative: Dexbrompheniramine 6 mg + pseudoephedrine 120 mg (sustained-release) twice daily. 4

Why First-Generation for Chronic Cough?

First-generation antihistamines work through anticholinergic properties that reduce secretions and suppress inflammatory mediators triggering the cough reflex—not through antihistamine effects. 4 Second-generation antihistamines lack these anticholinergic properties and are completely ineffective for upper airway cough syndrome. 4, 5

Contraindications to Decongestant Combinations

Absolute contraindications include: 4

• Narrow-angle glaucoma
• Symptomatic benign prostatic hypertrophy or urinary retention
• Severe uncontrolled hypertension
• Congestive heart failure

Expected Timeline

Improvement typically occurs within a few days to 2 weeks of starting treatment. 4 If no response after 2 weeks, obtain sinus imaging to evaluate for chronic sinusitis and consider alternative diagnoses such as asthma or gastroesophageal reflux disease. 4

For Acute Viral Upper Respiratory Infection (Common Cold)

If you have an acute viral infection with sore throat, nasal congestion, and cough lasting less than 2 weeks:

First-generation antihistamine + decongestant combinations are most effective. 5

• Brompheniramine 12 mg + pseudoephedrine 120 mg twice daily provides the best symptomatic relief. 5
• NSAIDs (ibuprofen, naproxen) significantly improve headache, ear pain, muscle pain, and sneezing. 5
• Antibiotics provide no benefit for viral infections and cause significant adverse effects—they should be avoided entirely. 5

Second-generation antihistamines (loratadine, fexofenadine, cetirizine) are ineffective for acute viral cough and should not be used. 5

Critical Pitfall to Avoid

Do not confuse allergic rhinitis with throat infection. If you have fever, severe throat pain, difficulty swallowing, or white patches on your tonsils, you may have bacterial pharyngitis (strep throat) requiring antibiotics, not antihistamines. Antihistamines treat allergy symptoms and post-nasal drip, not infections.