Sinus infection antibiotics are usually unnecessary: the US Centers for Disease Control and Prevention (CDC) estimates that 90–98% of acute rhinosinusitis cases are viral. Antibiotics do not treat viruses, and even when bacteria are involved, they may not help. The pattern of your symptoms—how long they last, how severe they are and whether they improve before worsening—can help a clinician decide whether to wait, reassess or prescribe treatment.
When Symptoms Point More Toward Bacterial Sinusitis
Facial pressure, a blocked or runny nose, cough and headache can occur with viral or bacterial illness. No single symptom, including thick or discoloured mucus, confirms a bacterial infection. For adults, US CDC guidance identifies three patterns that raise suspicion:
- Persistent symptoms: nasal discharge or daytime cough lasting more than 10 days without improvement.
- Severe symptoms: fever of at least 39°C (102°F), together with purulent nasal discharge or facial pain, for more than 3–4 days.
- Worsening after improvement: new or worsening fever, cough or nasal discharge after an initial viral illness had begun to get better.
These are clinical clues, not a home test. A clinician considers the full course of illness and your health; routine sinus X-rays are not recommended for uncomplicated cases in the CDC guidance.
Sinus Infection Antibiotics: When Waiting Can Be Reasonable
Meeting a pattern that suggests bacterial sinusitis does not automatically mean you need an antibiotic immediately. For uncomplicated adult cases, CDC guidance encourages watchful waiting when reliable follow-up is available. That means monitoring symptoms and arranging reassessment if you do not improve or you get worse—not simply ignoring persistent illness.
Antibiotics can cause side effects and contribute to antibiotic resistance. If symptoms are mild and you are stable, ask your clinician what timeframe to use for follow-up and what changes should prompt an earlier call. Children need age-specific assessment: CDC guidance allows up to three days of watchful waiting for children with persistent symptoms, but recommends antibiotics for severe or worsening disease.
When Antibiotics May Be Prescribed
If a clinician decides an adult has acute bacterial sinusitis, US CDC guidance lists amoxicillin or amoxicillin-clavulanate as first-line options. The right choice depends on individual factors, including allergies and local recommendations. For people with penicillin allergy, the CDC lists doxycycline or certain respiratory fluoroquinolones as alternatives; these are not medicines to start from a leftover prescription or choose without medical advice.
Azithromycin (often called a Z-Pak) is not recommended in that US guidance for bacterial sinusitis because resistance among Streptococcus pneumoniae is high—about 40%. Antibiotic recommendations can differ across health systems, and local resistance patterns matter. The CDC recommendations are for US outpatient care, not a universal prescription rule; if you live in the UK, EU, Australia or elsewhere, follow local clinical guidance rather than assuming the same drug is appropriate.
Know When to Get Medical Help
Arrange a medical review if symptoms last more than 10 days without improvement, become worse after starting to ease, or include the severe fever-and-pain pattern above. Seek urgent assessment for swelling or redness around an eye, changes in vision, a severe headache, confusion, a stiff neck or rapid, marked deterioration. This list is not exhaustive: get help for any symptom that feels severe or concerning.
If you are unsure whether to wait or seek care, contact a healthcare professional—especially for a child, someone with significant health conditions or symptoms that are getting worse. A clinician can weigh symptom timing and severity against your circumstances and explain whether watchful waiting, further assessment or an antibiotic is appropriate.
