For most sinus infections that need an antibiotic, amoxicillin (with or without clavulanate) is the recommended first-line choice. But here’s the more important point: roughly 90% to 98% of sinus infections are caused by viruses, which means antibiotics won’t help at all in the vast majority of cases. The “best” antibiotic is often no antibiotic, unless your symptoms meet specific criteria that point to a bacterial cause.
Most Sinus Infections Don’t Need Antibiotics
The overwhelming majority of acute sinus infections are viral. Only about 2% to 10% of people who visit a doctor for sinus symptoms actually have a bacterial infection. A viral sinus infection and a bacterial one can feel remarkably similar: congestion, facial pressure, thick nasal discharge, headache. The difference usually comes down to how long symptoms last and how they behave over time.
A study from Washington University School of Medicine illustrates this well. Researchers gave 166 adults with acute sinus infections either amoxicillin or a placebo for 10 days. At day three, there was no difference between the two groups. By day seven, the antibiotic group showed a tiny improvement on symptom questionnaires, but it wasn’t enough to represent noticeable relief. By day 10, about 80% of patients in both groups reported their symptoms were “very much improved” or cured. The takeaway: most sinus infections resolve on their own regardless of antibiotics.
When Antibiotics Are Actually Warranted
Three specific patterns suggest a bacterial sinus infection rather than a viral one:
- Persistent symptoms: Congestion, facial pain, or nasal discharge lasting 10 days or more without any improvement.
- Severe onset: A fever of 102°F or higher along with nasal discharge and facial pain lasting three to four days.
- Double worsening: Symptoms that start to improve after four to seven days, then suddenly get worse again.
If your symptoms fit one of these patterns, a bacterial cause is more likely and antibiotics make sense. If your sinus infection is only a few days old and gradually improving, waiting it out is the evidence-based approach.
Amoxicillin Is the First Choice
When antibiotics are appropriate, guidelines from the Infectious Diseases Society of America and the American Academy of Family Physicians recommend amoxicillin, with or without clavulanate, as first-line therapy. Clavulanate is an ingredient that helps amoxicillin work against bacteria that have developed basic resistance. Your doctor may choose the version with clavulanate if you’ve recently taken antibiotics, if your symptoms are severe, or if you live in an area with higher resistance rates.
A typical course lasts 5 to 10 days. Shorter courses are increasingly favored for uncomplicated cases because they reduce side effects and the risk of contributing to antibiotic resistance, while still being effective.
Options If You’re Allergic to Penicillin
Amoxicillin is a penicillin-type antibiotic, so it’s off the table if you have a penicillin allergy. The main alternatives include:
- Trimethoprim/sulfamethoxazole: Taken twice daily for about 10 days.
- Azithromycin: A shorter course, typically three days.
- Clarithromycin: Taken for about 14 days.
Azithromycin’s short course makes it appealing, but resistance among common sinus bacteria has been rising, which can make it less reliable. Your doctor will weigh local resistance patterns when choosing among these options.
Why Stronger Antibiotics Aren’t Better
You might assume a more powerful antibiotic would clear things up faster, but for sinus infections, that logic doesn’t hold. Fluoroquinolones (sometimes called “respiratory fluoroquinolones”) are broad-spectrum antibiotics that are sometimes prescribed for sinusitis, but the FDA has explicitly warned against using them when other options exist. These drugs carry risks of serious side effects involving tendons, muscles, joints, nerves, and the central nervous system. Some of these effects can be disabling and permanent.
The FDA’s position is clear: for acute sinusitis, the serious risks of fluoroquinolones generally outweigh the benefits when safer alternatives are available. They should only be considered for patients who truly have no other treatment options.
What About Children?
The same general principles apply to kids. Amoxicillin, with or without clavulanate, remains the first-line antibiotic for children with bacterial sinusitis. The dosage is calculated based on your child’s weight, so your pediatrician will determine the right amount. The diagnostic criteria are similar: persistent symptoms without improvement, high fever with discharge, or the double-worsening pattern.
What to Do While You Wait It Out
Whether or not you end up needing antibiotics, symptom management is the same. Saline nasal rinses help flush out mucus and reduce congestion. Over-the-counter pain relievers can address facial pressure and headaches. Staying hydrated thins mucus and makes it easier to drain. A warm compress across your cheeks and forehead can provide temporary relief from pressure.
Decongestant nasal sprays can help in the short term, but using them for more than three consecutive days can cause rebound congestion that makes things worse. Oral decongestants are another option, though they can raise blood pressure and cause restlessness in some people.
If you’ve been managing symptoms at home and hit the 10-day mark without improvement, or if you develop a high fever or worsening symptoms after an initial improvement, that’s when it makes sense to see your doctor and discuss whether antibiotics are the right next step.