Amoxicillin-clavulanate is the recommended first-line antibiotic for bacterial sinus infections in both adults and children. It’s preferred over plain amoxicillin because the added clavulanate helps it work against a broader range of bacteria, including strains that have developed resistance. But before reaching for any antibiotic, the more important question is whether you actually need one.
Most Sinus Infections Don’t Need Antibiotics
The vast majority of sinus infections are caused by viruses, not bacteria, and antibiotics do nothing against viruses. A bacterial sinus infection is likely only if your symptoms meet specific criteria: they’ve lasted 10 days or more without improvement, you have a fever of 102°F or higher along with nasal discharge and facial pain lasting three to four days, or your symptoms initially improved after four to seven days and then got worse again.
If your sinus infection doesn’t fit any of those patterns, it’s almost certainly viral. It will resolve on its own, typically within seven to ten days. Taking antibiotics unnecessarily exposes you to side effects like diarrhea and yeast infections while contributing to antibiotic resistance.
Why Amoxicillin-Clavulanate Is First Choice
Infectious disease guidelines recommend amoxicillin-clavulanate over plain amoxicillin and over stronger antibiotics like fluoroquinolones. The reasoning is straightforward: it’s effective against the three bacteria most commonly responsible for sinus infections, it has a well-understood safety profile, and it’s inexpensive. Using a narrower-spectrum antibiotic when possible helps preserve the effectiveness of stronger drugs for situations that truly require them.
High-dose amoxicillin-clavulanate is recommended in certain situations where resistant bacteria are more likely. This includes people who live in areas where more than 10% of the local pneumococcal bacteria are resistant to standard doses, anyone who has used antibiotics in the past month, adults over 65, children under two or those in daycare, people who were recently hospitalized, and those with weakened immune systems. Your provider will know whether your area has high resistance rates.
If You’re Allergic to Penicillin
Amoxicillin-clavulanate is a penicillin-type drug, so it’s off the table if you have a penicillin allergy. Several alternatives work well. Doxycycline is a common choice for adults. For both adults and children, certain cephalosporin antibiotics are options, including cefdinir, cefpodoxime, and cefuroxime. In a clinical trial comparing cefdinir to the fluoroquinolone levofloxacin, cure rates were 83% and 86% respectively, meaning cefdinir performed just as well as the stronger drug for moderate to severe bacterial sinus infections.
It’s worth noting that many people who believe they’re allergic to penicillin actually aren’t. If your allergy was diagnosed in childhood or based on a mild reaction, allergy testing can clarify whether you can safely take penicillin-type drugs, which opens up the most effective first-line option.
How Long You’ll Take Them
For adults, a five-to-seven-day course is standard. A large meta-analysis of 12 randomized trials found no difference in cure rates or relapse rates between short courses (three to seven days) and longer courses (six to ten days). Shorter courses also came with fewer side effects. Many providers prescribe seven days and advise patients they can stop after five if symptoms have clearly improved.
Children typically need a longer course of 10 to 14 days. Pediatric dosing is weight-based, so the prescription will be tailored to your child’s size.
When the First Antibiotic Doesn’t Work
You should start feeling noticeably better within 48 to 72 hours of starting antibiotics. If your symptoms haven’t budged by that point, the initial antibiotic may not be covering the specific bacteria involved. Your provider will typically switch to a different class of antibiotic. If you started on amoxicillin-clavulanate, the next step is often a respiratory fluoroquinolone or a higher-dose regimen. If you started on a non-penicillin alternative, your provider may try a different class altogether.
Persistent or recurring sinus infections, especially four or more episodes a year, may point to an underlying issue like nasal polyps, a structural blockage, or allergies that keep the sinuses chronically inflamed. Imaging or a referral to an ear, nose, and throat specialist can help identify the cause.
What Else Helps Alongside Antibiotics
Saline nasal irrigation, whether from a squeeze bottle or neti pot, is one of the most consistently supported add-on treatments. It physically flushes mucus and irritants from the sinuses, reduces swelling, and can noticeably improve comfort. Using it alongside antibiotics tends to speed symptom relief.
Nasal corticosteroid sprays can also reduce inflammation in the sinus passages. These are available over the counter and are most helpful if allergies or chronic inflammation are contributing to the problem. For an acute bacterial infection, they’re a useful complement to antibiotics but not a replacement. Over-the-counter decongestant sprays provide short-term relief but should be limited to three days to avoid rebound congestion that makes things worse.