What Antibiotic Is Used to Treat a Sinus Infection?

Amoxicillin-clavulanate is the most widely recommended antibiotic for a bacterial sinus infection in both adults and children. But here is the part that surprises most people walking into a doctor’s office with a stuffed-up, aching face: the vast majority of sinus infections are caused by viruses, not bacteria, and no antibiotic will help with those. Understanding which antibiotic works, when it is actually warranted, and what the alternatives look like if the first choice fails turns out to be more layered than a simple prescription might suggest.

Most Sinus Infections Do Not Need an Antibiotic at All

Roughly nine out of ten acute sinus infections are viral. They feel miserable, they produce thick discolored mucus, and they drag on for a week or more, but they resolve on their own. The color or thickness of your nasal discharge does not reliably tell you whether bacteria are involved. A systematic review found that using purulent (yellowish-green) mucus as a sign to prescribe antibiotics is not supported by evidence, and the decision to treat should not hinge on its presence alone.¹ That is worth knowing, because many people assume green mucus automatically means they need antibiotics.

Doctors generally suspect a bacterial sinus infection when symptoms last more than ten days without improving, when symptoms start to get better and then suddenly worsen again, or when the infection hits hard right from the start with a high fever and severe facial pain persisting for several days. Those patterns raise the probability that bacteria have set up shop in the sinuses, and that is when antibiotics enter the picture.

Why Amoxicillin-Clavulanate Is the First Choice

When a bacterial sinus infection is confirmed or strongly suspected, amoxicillin-clavulanate is the standard first-line antibiotic across most guidelines. Plain amoxicillin used to be the default, and some clinicians still prescribe it for mild, uncomplicated cases. The addition of clavulanate gives the drug broader coverage against bacteria that have developed resistance to basic penicillin-type antibiotics, particularly strains that produce enzymes capable of breaking down amoxicillin on its own.

The typical adult dose is either standard-dose or high-dose amoxicillin-clavulanate, with the high-dose version reserved for situations where resistance is more likely. Risk factors for resistant bacteria include recent antibiotic use within the past month, living in an area with high rates of antibiotic-resistant organisms, attending or working in daycare, and having other health conditions that complicate treatment.

For people with a true penicillin allergy, the picture changes. Doxycycline is often recommended as an alternative for adults. Respiratory fluoroquinolones like levofloxacin or moxifloxacin are another option, though they carry a heavier side-effect profile and are generally saved for more complicated situations. In children with penicillin allergies, choices narrow further and often involve certain cephalosporins (which are chemically related to penicillins but tolerated by most people with mild penicillin sensitivities) or, in some cases, clindamycin combined with a third-generation cephalosporin.

How Long the Course Should Last

The traditional prescription for a sinus infection runs ten days. But the evidence increasingly supports shorter courses. A meta-analysis covering twelve randomized trials and over 4,400 patients found that short-course antibiotic treatment (three to seven days) had the same clinical success rate as longer courses (six to ten days), with no difference in relapses or bacterial clearance.² When the analysis specifically compared five-day regimens against ten-day regimens, effectiveness remained equivalent, while side effects were fewer with the shorter course.

A separate review of clinical trials reached the same conclusion, finding that five-day courses with various antibiotic classes showed equivalent efficacy to ten-day courses for uncomplicated acute sinusitis in adults.³ The practical takeaway is that if your doctor prescribes a five-day course, that is not cutting corners. It reflects where the evidence has moved. Shorter courses mean fewer side effects, less disruption to your gut bacteria, and lower risk of breeding resistant organisms.

That said, some patients with severe symptoms, immunocompromised states, or complicated infections still get prescribed the full ten-day or even longer courses. The short-course data applies specifically to uncomplicated cases.

Treating Sinus Infections in Children

Children get bacterial sinus infections, too, though diagnosing them can be trickier because kids often have overlapping viral colds and cannot always describe their symptoms precisely. The current consensus for uncomplicated acute bacterial sinusitis in children is amoxicillin-clavulanate at a standard dose of 45 mg/kg/day.⁴ Plain amoxicillin at a higher dose of 90 mg/kg/day is an alternative when resistance is not a concern. For children at risk of resistant bacteria or with severe disease, the recommendation shifts to high-dose amoxicillin-clavulanate at 90 mg/kg/day.

A few practical notes for parents. Kids often resist the taste of liquid amoxicillin-clavulanate, so mixing it with something flavored or keeping it cold can help. The clavulanate component is the ingredient most likely to cause diarrhea and stomach upset, and the higher the proportion of clavulanate, the worse those side effects tend to be. That is why the high-dose formulations are designed to increase only the amoxicillin portion while keeping clavulanate steady.

Antibiotics During Pregnancy

Sinus infections during pregnancy are not uncommon. Hormonal changes cause nasal congestion and swelling that predispose the sinuses to infection. When antibiotics are genuinely needed, the safest classes are penicillins and cephalosporins. A systematic review of management during pregnancy recommended that antibiotics like tetracyclines, aminoglycosides, trimethoprim-sulfamethoxazole, and fluoroquinolones should be avoided because of potential harm to the fetus.⁵ That rules out doxycycline and levofloxacin, two of the common alternatives for penicillin-allergic patients, which means pregnant individuals with penicillin allergies need careful discussion with their provider about safe options.

The same review noted that long-term use of macrolides (like azithromycin) or doxycycline for chronic sinusitis is not recommended during pregnancy. For acute episodes, the emphasis is on confirming that bacterial infection is actually present before prescribing, since unnecessary antibiotic exposure during pregnancy carries its own risks.

The Wait-and-See Prescription

One approach that has gained traction is the delayed or “wait-and-see” prescription. Your doctor writes the antibiotic prescription but asks you to hold off on filling it for a few days to see if symptoms improve on their own. If they do, you skip the antibiotics entirely. If they worsen or persist, you fill the prescription without needing another appointment.

A survey of general practitioners found that sinusitis was the most common diagnosis for which doctors issued a delayed prescription, at about a third of cases. Among patients given a delayed prescription, fewer than half ended up actually taking the antibiotics.⁶ Doctors also rated sinusitis as the diagnosis where they found delayed prescribing most reasonable. This strategy works because many cases that initially look like they could be bacterial resolve before the antibiotics are needed, saving the patient unnecessary drug exposure while still keeping the safety net in place.

A pharmacoeconomic review found that this symptomatic-treatment-first approach, where antibiotics are given only if patients fail to improve after about seven days, was the most cost-effective strategy compared to treating everyone empirically with antibiotics right away.⁷ That matters beyond individual cost savings. Reducing unnecessary antibiotic prescriptions at scale slows the development of resistant bacteria in the community.

What Antibiotics Do to Your Gut

Even a short course of antibiotics for a sinus infection does not stay local to your sinuses. Oral antibiotics travel through your entire system and alter your gut microbiome. Research on patients with chronic sinusitis found that repeated antibiotic treatments reduced the numbers of many gut bacterial species, and restoring the gut to its previous state could take up to four years.⁸ That finding came from patients who had not used antibiotics for at least a month before testing, suggesting the disruption lingers well beyond the treatment period.

The picture is somewhat more reassuring for single short courses. A study of patients taking once-daily oral antibiotics for a week found no significant major shifts in gut bacterial communities or diversity over that period, though there was a trend toward reduced diversity that did not reach statistical significance.⁹ One week of a single antibiotic does not appear to cause a dramatic gut upheaval, but cumulative courses over months or years are a different story. This is part of why the growing consensus around shorter treatment durations matters. Five days of amoxicillin-clavulanate is less disruptive than ten, and skipping antibiotics entirely when a viral infection is the real culprit avoids the gut disruption altogether.

When Sinus Infections Get Dangerous

Left untreated, bacterial sinusitis rarely but occasionally leads to serious complications. The sinuses sit close to the eyes and the brain, separated by thin bone. When infection erodes through those barriers, the consequences can be severe. Orbital complications, including abscess formation around the eye, are among the more common serious outcomes. Intracranial complications are rarer but more dangerous.¹⁰

The most feared intracranial complication is subdural empyema, a collection of pus between the brain and its outer covering. A case series reviewing frontal sinusitis complications reported that subdural empyema carries a mortality rate ranging from about 10% to 70%, depending on how quickly it is identified and treated. Among survivors, roughly a third experienced lasting weakness on one side of the body, and residual neurological problems occurred in close to half of cases.¹¹ A case report documented one patient with frontal sinusitis who developed subdural empyema, progressed to brain herniation within 24 hours of admission, developed jugular vein blood clots with infected clots traveling to the lungs, and ultimately died on the second hospital day.¹²

These outcomes are genuinely rare for garden-variety sinus infections, and this section is not meant to provoke panic about a stuffy nose. But they illustrate why bacterial sinusitis, once confirmed, warrants appropriate treatment, and why worsening symptoms like severe headache, high fever, visual changes, or facial swelling after a sinus infection should prompt urgent medical attention.

Sinus Infections That Start in Your Teeth

Not all sinus infections start with a cold. The roots of your upper back teeth sit remarkably close to the floor of the maxillary sinus, and dental infections can punch through into the sinus directly. This is called odontogenic sinusitis, and it behaves differently from the standard version. The bacteria involved tend to come from oral flora rather than the typical respiratory pathogens, which means the usual five-to-ten-day course of amoxicillin-clavulanate may not be enough. Management typically involves a three-to-four-week course of antibiotics effective against oral bacteria, along with treatment of the underlying dental problem.¹³

If you have a sinus infection that keeps coming back on one side, responds poorly to standard antibiotics, or is associated with recent dental work or a toothache in your upper jaw, odontogenic sinusitis is worth raising with your doctor. It is often overlooked because the sinus symptoms overshadow the dental source, and treating the sinus alone without addressing the tooth will not resolve the problem.

Antibiotic Resistance in Chronic Cases

For people dealing with chronic sinusitis, the antibiotic landscape becomes more complicated. Chronic infections involve different bacterial profiles than acute ones, and repeated courses of antibiotics can select for resistant organisms. A study of bacteria isolated from patients with chronic sinusitis found high rates of multidrug resistance. Among the gram-negative bacteria recovered, over three-quarters were multidrug resistant, and among gram-positive isolates, roughly three-quarters showed the same pattern. Staphylococcus aureus was the most resistant gram-positive organism, with 90% of isolates classified as multidrug resistant.¹⁴

These numbers come from a single-center study and reflect the worst-case population, patients whose chronic infections had already failed multiple treatments. They should not be taken as representative of what happens with a first acute sinus infection. But they do illustrate why infectious disease specialists push back against the habit of prescribing antibiotics for every sinus complaint. Every unnecessary course contributes, in a small way, to the selection pressure that breeds resistant strains.

Reducing Unnecessary Prescriptions Without Reducing Patient Satisfaction

One of the persistent challenges in managing sinus infections is that patients often arrive at the clinic expecting an antibiotic and feel unsatisfied if they leave without one. A pilot program tested a telemedicine care bundle designed to guide clinicians through evidence-based sinusitis management and patient communication. After implementation, antibiotic prescribing for sinusitis dropped measurably even as the number of patients receiving a sinusitis diagnosis increased. Notably, negative patient survey responses also decreased, meaning patients were not less satisfied when the visit ended with symptom management advice rather than a prescription.¹⁵

The implication is that much of the over-prescribing happens because clinicians assume patients will be unhappy without antibiotics, not because patients are actually demanding them. When the rationale for watchful waiting is explained clearly, most people are comfortable with it. If your doctor tells you that your sinus infection does not need antibiotics right now, that is not dismissiveness. It is an evidence-based call that spares you side effects, protects your gut microbiome, and saves antibiotic effectiveness for when it is genuinely needed.