Amoxicillin is the first-line antibiotic for a bacterial sinus infection, typically prescribed as 500 mg three times daily for 5 to 10 days. But most sinus infections are viral, which means antibiotics won’t help at all. The key question isn’t just which antibiotic to take, but whether you actually need one.
When Antibiotics Are Actually Needed
The vast majority of sinus infections start as viral illnesses and clear up on their own within 7 to 10 days. Antibiotics only help when bacteria are the cause, and there’s no quick test to distinguish viral from bacterial sinusitis. Instead, the diagnosis is based on how long your symptoms last and how they behave.
Antibiotics are generally appropriate in three scenarios: your symptoms persist for 10 days or more without improvement, your symptoms initially improve and then suddenly worsen (sometimes called “double worsening”), or you develop severe symptoms like a high fever above 102°F (39°C) along with facial pain and thick nasal discharge lasting at least 3 to 4 consecutive days. If your symptoms don’t fit one of those patterns, you’re likely dealing with a viral infection that will resolve with rest, fluids, and over-the-counter symptom relief.
First-Line Antibiotic: Amoxicillin
For uncomplicated bacterial sinusitis in adults, amoxicillin is the standard starting point. The typical regimen is 500 mg taken three times a day. Some providers prescribe amoxicillin-clavulanate instead, which pairs amoxicillin with an ingredient that helps it work against bacteria that have developed basic resistance. This combination is often preferred when resistance is a concern or symptoms are more severe.
Treatment courses generally run 5 to 10 days, with 10 days being the traditional recommendation. However, research has shown that shorter courses of 3 to 7 days can be equally effective for straightforward cases. Your provider will decide based on how severe your symptoms are and how quickly you respond.
If You’re Allergic to Penicillin
Since amoxicillin belongs to the penicillin family, it’s off the table if you have a penicillin allergy. In that case, doxycycline or a respiratory fluoroquinolone (such as moxifloxacin or levofloxacin) are the recommended alternatives. Moxifloxacin is FDA-approved for acute bacterial sinusitis at a dose of 400 mg once daily for 10 days.
Fluoroquinolones carry a higher risk of side effects, including tendon problems and nerve damage, so they’re typically reserved for situations where safer options aren’t suitable. Your provider will weigh the risks against the severity of your infection.
Why Azithromycin Isn’t Recommended
You might expect a Z-pack (azithromycin) to be a go-to option, since it’s one of the most commonly prescribed antibiotics. But current guidelines specifically recommend against using azithromycin or other macrolide antibiotics for sinus infections. The reason is straightforward: the bacteria most commonly responsible for sinusitis, particularly Streptococcus pneumoniae, have developed high rates of resistance to these drugs. The same applies to trimethoprim-sulfamethoxazole (Bactrim). Using either of these means a meaningful chance the antibiotic simply won’t work.
What to Expect During Treatment
Most people start feeling noticeably better within 3 to 5 days of starting antibiotics. If you see no improvement after 3 to 5 days, contact your provider. This could mean the bacteria causing your infection are resistant to the antibiotic you’re taking, or that the diagnosis needs to be reconsidered. Your provider may switch to a different antibiotic or order imaging to get a better look at what’s going on.
Finish the full course you’re prescribed, even if you feel better early. Stopping short can allow surviving bacteria to rebound, potentially causing a harder-to-treat infection.
Antibiotics for Children
Children with bacterial sinusitis follow a similar playbook, but the dosing is weight-based. The current consensus recommends amoxicillin-clavulanate as first-line treatment at a standard dose based on body weight, divided into two daily doses. For kids at higher risk of antibiotic resistance or those with more severe symptoms, the amoxicillin dose is doubled.
Children with a severe penicillin allergy (anaphylaxis) are typically given levofloxacin instead. Those with milder penicillin allergies, like a delayed rash, can often safely take certain cephalosporin antibiotics as alternatives. For children who can’t keep oral medication down due to vomiting, an injectable antibiotic can be given once daily until they can switch to pills or liquid.
Supportive Care Alongside Antibiotics
Antibiotics target the infection itself, but they won’t relieve your congestion, pressure, or pain directly. While the medication works, several things can make you more comfortable. Saline nasal irrigation (using a neti pot or squeeze bottle) helps flush out mucus and reduce swelling. Over-the-counter pain relievers like ibuprofen or acetaminophen manage facial pain and headaches effectively. A nasal corticosteroid spray can reduce inflammation in the nasal passages, helping you breathe and drain more easily.
Decongestant sprays like oxymetazoline provide quick relief but shouldn’t be used for more than 3 days, since longer use causes rebound congestion that can make things worse. Staying well-hydrated and using a humidifier, especially at night, helps keep mucus thin and easier to clear.