The first-line antibiotic for a bacterial sinus infection is amoxicillin-clavulanate, a combination of amoxicillin plus a compound that helps it work against resistant bacteria. But most sinus infections are viral, meaning antibiotics won’t help at all. Knowing which situation you’re in matters more than knowing which pill to take.
Most Sinus Infections Don’t Need Antibiotics
Around 90% of sinus infections start as viral illnesses, essentially a cold that inflames the sinuses. These resolve on their own within 7 to 10 days. Antibiotics do nothing against viruses, and taking them unnecessarily contributes to antibiotic resistance.
A sinus infection is likely bacterial, and worth treating with antibiotics, in three specific scenarios:
- Persistent symptoms: Nasal congestion, discharge, or daytime cough lasting more than 10 days without any improvement.
- Severe onset: A fever of 102°F or higher along with thick, discolored nasal discharge and facial pain lasting at least 3 consecutive days.
- Double worsening: Symptoms that seem to improve after 4 to 7 days, then suddenly get worse again with new fever, worsening congestion, or increased cough.
If none of these patterns fit, you’re almost certainly dealing with a viral infection. Your doctor may recommend watchful waiting rather than prescribing antibiotics right away, even if your mucus is green or yellow (color alone doesn’t indicate a bacterial infection).
First-Line Antibiotic: Amoxicillin-Clavulanate
When antibiotics are warranted, amoxicillin-clavulanate is the preferred choice for both adults and children. It’s favored over plain amoxicillin because the added clavulanate helps overcome resistance from bacteria that have learned to break down standard amoxicillin. The three most common bacteria behind sinus infections are well covered by this combination.
A higher dose version is recommended for people at greater risk of resistant bacteria. That includes anyone who has used antibiotics in the past month, people over 65, those with weakened immune systems, anyone recently hospitalized, and children in daycare. If you live in an area where resistant strains of the most common sinus bacteria are prevalent (above 10% of cases), your doctor may also start with the higher dose.
Alternatives If You’re Allergic to Penicillin
Since amoxicillin-clavulanate is a penicillin-based drug, it’s off the table if you have a penicillin allergy. For adults, there are two main alternatives:
- Doxycycline: Highly active against the bacteria that cause sinus infections and considered a solid substitute. It’s the preferred non-penicillin option for many doctors.
- Respiratory fluoroquinolones (levofloxacin, moxifloxacin): Effective but generally reserved for situations where other options won’t work, because fluoroquinolones carry a higher risk of side effects including tendon problems and nerve damage.
For children with a penicillin allergy, levofloxacin is one option. Another approach combines clindamycin with a third-generation cephalosporin, which covers a broader range of bacteria.
Why Azithromycin Is No Longer Recommended
If you’ve been prescribed a Z-Pack (azithromycin) for a sinus infection in the past, that’s now considered outdated. Azithromycin belongs to a class of antibiotics called macrolides, and resistance to these drugs has climbed dramatically. Nearly 38% of the most common sinus-infection bacteria are now resistant to macrolides, and that number has been rising by almost 2% per year. At those resistance levels, there’s a meaningful chance the antibiotic simply won’t work. Current guidelines from the Infectious Diseases Society of America do not recommend azithromycin or other macrolides for bacterial sinus infections.
How Long You’ll Take Antibiotics
For adults, the typical course is 5 to 7 days. Some guidelines extend the range to 5 to 10 days depending on how severe the infection is and whether you have risk factors for complications. Children generally need a longer course of 10 to 14 days.
You should start feeling noticeably better within 3 days of starting antibiotics. If there’s no improvement by 72 hours, that’s a signal something else may be going on. Your doctor may want imaging to check for complications or may switch you to a different antibiotic.
Nasal Steroid Sprays Alongside Antibiotics
Using a nasal corticosteroid spray while taking antibiotics can improve your symptoms faster than antibiotics alone. These sprays reduce the swelling inside your nasal passages, which helps your sinuses drain and relieves pressure and congestion. Over-the-counter options are widely available, and studies have consistently shown they provide meaningful additional symptom relief when paired with antibiotic treatment. Saline rinses (like a neti pot or squeeze bottle) can also help flush mucus and keep passages open.
Signs the Infection May Be Spreading
Bacterial sinus infections rarely become dangerous, but the sinuses sit close to the eyes and brain, so an infection that spreads beyond them can become serious quickly. Seek emergency care if you develop swelling around your eyes, vision changes, a stiff neck, persistent vomiting, confusion, or a high fever lasting more than 3 days despite being on antibiotics. These symptoms can indicate the infection has reached the eye socket or the tissue surrounding the brain, both of which require more aggressive treatment in a hospital setting.