The first-line antibiotic for a bacterial sinus infection is amoxicillin-clavulanate, commonly sold as Augmentin. It combines a standard penicillin-type antibiotic with a second ingredient that helps it work against resistant bacteria. But most sinus infections are viral, not bacterial, which means antibiotics won’t help the majority of people with sinus symptoms. Knowing when antibiotics are actually warranted is just as important as knowing which one to take.
Most Sinus Infections Don’t Need Antibiotics
Around 90% of sinus infections start as viral illnesses, and viral infections clear up on their own without antibiotics. The tricky part is that bacterial and viral sinus infections look almost identical in the first few days: congestion, facial pressure, thick nasal discharge, and sometimes a low fever.
Guidelines from the Infectious Diseases Society of America identify three patterns that suggest a bacterial infection worth treating:
- Persistent symptoms: Congestion, facial pain, or nasal discharge lasting 10 days or more without improvement.
- Severe onset: A fever of 102°F or higher along with facial pain and discolored nasal discharge lasting three to four days.
- Double worsening: Symptoms that start improving after four to seven days, then suddenly get worse again.
If your symptoms don’t fit any of these patterns, you likely have a viral infection, and taking an antibiotic won’t speed your recovery. It can, however, cause side effects and contribute to antibiotic resistance.
First-Line Antibiotic for Adults
When a bacterial sinus infection is confirmed or strongly suspected, amoxicillin-clavulanate is the standard choice for adults. The typical dose is 875 mg/125 mg taken twice a day. This combination is preferred over plain amoxicillin because the clavulanate component overcomes a common defense mechanism that some sinus bacteria use to resist treatment.
A standard course lasts seven to ten days, though some newer shorter regimens exist. Most people start feeling noticeably better within 48 to 72 hours of starting treatment. If your symptoms haven’t improved at all after three to five days on the antibiotic, that’s a signal to contact your prescriber, as you may need a different medication.
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. The alternative depends on how severe your infection is.
For mild bacterial sinusitis, doxycycline is a well-established option, taken as 100 mg twice daily. Trimethoprim-sulfamethoxazole (Bactrim) is another cost-effective choice. Both cover the bacteria most commonly responsible for sinus infections without involving penicillin.
For moderate or more severe infections in people with penicillin allergies, fluoroquinolone antibiotics like levofloxacin or moxifloxacin are typically prescribed. These are broad-spectrum antibiotics that are highly effective but carry a higher risk of side effects, so they’re generally reserved for situations where simpler options won’t work.
Why Z-Packs Aren’t Ideal
Many people expect to receive azithromycin (the “Z-Pack”) for a sinus infection, and it’s still occasionally prescribed. However, resistance rates among common sinus bacteria have climbed significantly over the past two decades, making azithromycin a less reliable choice. Current guidelines favor doxycycline or trimethoprim-sulfamethoxazole over azithromycin for mild infections in penicillin-allergic patients.
Antibiotics for Children
For kids with bacterial sinusitis, high-dose amoxicillin is the first-line treatment, dosed by weight at 80 to 90 mg per kilogram per day split into two doses. If a child has taken amoxicillin in the past month or isn’t improving on it, the step up is amoxicillin-clavulanate at the same weight-based dose.
Second-line options for children include cephalosporin antibiotics like cefdinir or cefuroxime. Doxycycline is an option only for children older than eight. The high-dose approach is recommended because more than 10% of the most common sinus bacteria in many regions have developed partial resistance to standard amoxicillin doses.
Nasal Steroid Sprays Help Antibiotics Work Better
Adding a nasal corticosteroid spray alongside your antibiotic can noticeably improve symptom relief. Research published in the Journal of Allergy and Clinical Immunology found that patients using a steroid nasal spray with their antibiotic had measurably better symptom scores than those on antibiotics alone. These sprays reduce the swelling inside your nasal passages, which helps your sinuses drain and allows the antibiotic to reach the infected tissue more effectively.
Over-the-counter options like fluticasone (Flonase) or triamcinolone (Nasacort) are widely available and can be started as soon as symptoms begin. Saline rinses or neti pots also help flush out mucus and are safe to use alongside both the spray and the antibiotic.
Recurring Infections May Need a Specialist
A single episode of bacterial sinusitis that responds to antibiotics is straightforward. But if you find yourself dealing with multiple bouts per year, or your symptoms drag on for 12 weeks or longer despite treatment, the problem may be chronic sinusitis. This is a different condition with different causes, often involving ongoing inflammation, nasal polyps, or structural issues rather than a simple bacterial infection that antibiotics can clear.
At that point, a referral to an ear, nose, and throat specialist or an allergist is the typical next step. They can use imaging and direct examination of your nasal passages to identify what’s keeping your sinuses from draining properly and recommend targeted treatment, which may or may not involve additional antibiotics.