Most sinus infections don’t need antibiotics at all. Between 90% and 98% of acute sinus infections are caused by viruses, which antibiotics can’t treat. When a sinus infection is bacterial, amoxicillin (with or without clavulanate) is the standard first-line antibiotic, typically prescribed for 5 to 10 days.
The challenge is figuring out whether your infection is one of the small percentage that’s actually bacterial. Understanding that distinction is the first step toward knowing which antibiotic, if any, makes sense.
Most Sinus Infections Don’t Need Antibiotics
A sinus infection usually starts the same way a cold does: congestion, facial pressure, thick nasal discharge, maybe a low fever. That’s because most sinus infections are viral, and they follow the same arc as a cold. They get worse over the first few days, plateau, and then gradually improve over one to two weeks. Taking antibiotics during a viral sinus infection won’t speed recovery, and it exposes you to side effects like diarrhea, rashes, and the broader problem of antibiotic resistance.
The CDC recommends seeing a healthcare provider if your symptoms last more than 10 days without improvement, or if they get worse after initially getting better. That “double worsening” pattern, where you start to feel better and then take a noticeable turn for the worse, is one of the clearest signals that bacteria may have moved in. A high fever (102°F or above) with thick, colored nasal discharge lasting three or more consecutive days can also point toward a bacterial cause. Without one of these patterns, antibiotics are unlikely to help.
First-Line Antibiotic: Amoxicillin
When your provider determines that antibiotics are warranted, amoxicillin is the go-to choice. It’s effective against the most common bacteria behind sinus infections, it’s inexpensive, and it has a well-established safety profile. For straightforward cases, a course of 5 to 10 days is the standard recommendation from major clinical guidelines.
In some situations, your provider may prescribe amoxicillin combined with clavulanate. The clavulanate component helps the antibiotic work against bacteria that have developed a defense mechanism against plain amoxicillin. This combination is more commonly chosen when you’ve had a sinus infection recently, when initial treatment didn’t work, or when symptoms are more severe. A typical adult dose for more serious infections is 875 mg of amoxicillin with 125 mg of clavulanate, taken every 12 hours.
For children, dosing is weight-based. Pediatric guidelines recommend high-dose amoxicillin-clavulanate at 90 mg per kilogram per day (based on the amoxicillin portion), split into two doses. Most children take a 7- to 10-day course, though severe infections or cases in children with weakened immune systems may call for 10 to 14 days.
Options if You’re Allergic to Penicillin
If you have a penicillin allergy, doxycycline is a common alternative for adults. The typical regimen is 200 mg on the first day, followed by 100 mg once daily for five more days. Doxycycline is not an option for children under 12.
Large reviews comparing different antibiotic classes for sinus infections, including penicillins, cephalosporins, macrolides, and tetracyclines like doxycycline, have found no major differences in how well they work. So while amoxicillin is preferred because of its cost and safety profile, alternatives are not considered less effective. Your provider will choose based on your allergy history, past antibiotic use, and local resistance patterns.
Why Fluoroquinolones Are a Last Resort
Antibiotics like levofloxacin and moxifloxacin (fluoroquinolones) are powerful and do treat sinus infections, but they carry serious risks that make them a poor choice when other options exist. The FDA has warned that the side effects of these drugs generally outweigh the benefits for sinus infections. Those side effects can involve tendons, muscles, joints, nerves, and the central nervous system, and in some cases the damage is permanent.
Fluoroquinolones should only be used for sinus infections when no alternative antibiotic is available. If a provider prescribes one without trying amoxicillin or doxycycline first, it’s worth asking why.
What to Expect During Treatment
Once you start antibiotics for a bacterial sinus infection, you should notice improvement within two to three days. Facial pressure and fever tend to improve first, while congestion and drainage can linger a bit longer. If you don’t feel any better after three to four days on antibiotics, contact your provider. That may mean the bacteria aren’t responding to the chosen drug and a switch is needed.
Finish the full course of antibiotics even if you feel better before the prescription runs out. Stopping early increases the chance that surviving bacteria will regroup and cause a relapse, potentially one that’s harder to treat. Side effects to watch for include stomach upset, diarrhea, and yeast infections. These are generally mild with amoxicillin but worth mentioning to your provider if they become bothersome.
Symptom Relief While You Wait
Whether your sinus infection is viral or bacterial, the same supportive measures help you feel better. Saline nasal rinses (using a squeeze bottle or neti pot with distilled or previously boiled water) physically flush mucus and reduce congestion. Over-the-counter nasal steroid sprays reduce inflammation in the sinus passages. Pain relievers like ibuprofen or acetaminophen help with facial pain and headache.
Decongestant nasal sprays provide fast relief but shouldn’t be used for more than three consecutive days, as longer use can cause rebound congestion that’s worse than what you started with. Oral decongestants are an option for slightly longer use but can raise blood pressure. Staying well hydrated and breathing warm, humidified air (a hot shower works well) help thin mucus and ease drainage.
These measures are often the only treatment needed. For the vast majority of sinus infections, time and symptom management are the real cure, and antibiotics are reserved for the small fraction that bacteria are driving.