Could the facial and neck rash with dry, itchy ears that began two days after completing a 5‑day course of oseltamivir (Tamiflu) for influenza be a delayed drug reaction, and what is the appropriate management?

Facial Rash After Tamiflu: Likely Delayed Hypersensitivity Reaction

This rash is most consistent with a delayed hypersensitivity reaction to oseltamivir (Tamiflu), and you should discontinue the medication permanently and manage the reaction symptomatically with antihistamines and topical corticosteroids.

Evidence Supporting Drug Reaction

The timing strongly suggests a delayed drug hypersensitivity reaction rather than a viral exanthem:

• Delayed cutaneous reactions to oseltamivir typically occur days to weeks after drug initiation, with the rash appearing 2 days after completing the 5-day course fitting this pattern 1
• Oseltamivir is listed among drugs causing delayed hypersensitivity reactions, including maculopapular exanthema and urticarial drug eruptions, which can manifest >6 hours to weeks after starting the medication 1
• The sunburn-like quality with pruritus and dry skin on ears is consistent with a delayed T-cell–mediated drug reaction rather than the typical viral exanthem pattern 1

Why This Is Likely NOT Influenza-Related

• The patient completed the full 5-day Tamiflu course one week ago, making ongoing viral symptoms extremely unlikely 1
• Influenza-related rashes typically appear during acute illness, not 9-10 days after symptom onset when viral shedding has ceased 2
• No fever or systemic symptoms are described, which would be expected with a viral exanthem 3

Documented Oseltamivir Dermatologic Reactions

While one large retrospective study found no increased risk of skin reactions with oseltamivir (adjusted rate ratio 1.05,95% CI: 0.88-1.24) 4, this does not exclude individual cases:

• Oseltamivir's main side effects are listed as nausea, vomiting, and gastrointestinal symptoms, with rash and ear disorders listed as "main side effects" in guideline tables 1
• Hypersensitivity reactions are documented as "rare side effects" of oseltamivir 1
• Post-marketing surveillance has identified allergic reactions including facial edema with neuraminidase inhibitors 1

Immediate Management Recommendations

Discontinue oseltamivir permanently and document this as a drug allergy:

• Oral antihistamines (cetirizine 10 mg daily or loratadine 10 mg daily) for pruritus 1
• Topical corticosteroids (hydrocortisone 1-2.5% or triamcinolone 0.1% cream) twice daily to affected areas for 5-7 days 1
• Emollients for dry skin on ears 1

Monitoring for Severe Reactions

Watch for warning signs of severe cutaneous adverse reactions (though unlikely given current presentation):

• Mucosal involvement (oral, ocular, genital lesions) would suggest Stevens-Johnson syndrome 1
• Fever, lymphadenopathy, or systemic symptoms developing would require urgent evaluation for DRESS syndrome 1, 3
• Facial edema progression or respiratory symptoms would necessitate emergency evaluation 1

Expected Clinical Course

• Delayed hypersensitivity rashes typically resolve within 1-2 weeks after drug discontinuation with symptomatic treatment 1
• Eczematous reactions may persist for several days and require continued topical therapy 1
• If the rash worsens or new symptoms develop after 48-72 hours, re-evaluate for alternative diagnoses 3

Future Influenza Management

• Document oseltamivir allergy in the medical record to prevent future exposure 1
• Zanamivir (inhaled) is an alternative neuraminidase inhibitor if future influenza treatment is needed, as cross-reactivity between oseltamivir and zanamivir is unlikely given different chemical structures 1
• Annual influenza vaccination remains the primary prevention strategy and is not contraindicated by oseltamivir allergy 1, 5

Critical Pitfall to Avoid

Do not assume this is a viral exanthem simply because the patient had influenza—the temporal relationship (rash onset 2 days after completing oseltamivir, 9-10 days after influenza onset) strongly favors drug reaction over viral etiology 1.