Penicillin and amoxicillin are the first-line antibiotics for bacterial tonsillitis, and they’ve held that position for decades. Group A Streptococcus, the bacteria behind most cases of bacterial tonsillitis, has never developed resistance to penicillin. For people allergic to penicillin, several effective alternatives exist, including certain cephalosporins, azithromycin, and clindamycin.
That said, antibiotics only work when the cause is bacterial. Most sore throats and tonsillitis cases are viral, and no antibiotic will help with those. A rapid strep test or throat culture confirms whether bacteria are involved before treatment starts.
How Doctors Decide You Need Antibiotics
Not every inflamed tonsil calls for antibiotics. Doctors use a set of clinical signs called the Centor criteria to gauge how likely your infection is bacterial. You get one point for each of these: fever at or above 38°C (100.4°F), no cough, swollen lymph nodes at the front of your neck, and white patches or swelling on your tonsils. The score ranges from 0 to 4.
A score of 3 or 4 means a bacterial cause is much more likely, but even then, guidelines recommend confirming with a rapid strep test or throat culture before prescribing antibiotics. A score below 3 makes strep unlikely enough that testing may still be done but empirical antibiotics are generally not recommended. In one study, every patient with confirmed Group A Strep had a score of 3 or 4, and none scored below 3.
Penicillin and Amoxicillin: The Standard Choice
Penicillin remains the treatment of choice because of its proven track record, narrow spectrum (meaning it targets the specific bacteria without wiping out as many helpful ones), safety profile, and low cost. Amoxicillin is in the same drug family and is often preferred in practice because it tastes better in liquid form for children and can be taken less frequently.
The standard course lasts 10 days. Most people start feeling noticeably better within two to three days, and bacterial symptoms can begin clearing as early as 48 hours after the first dose. It’s important to finish the full 10 days even once you feel fine. Stopping early leaves some bacteria alive, which increases the chance of the infection returning and contributes to antibiotic resistance over time.
Alternatives for Penicillin Allergies
If you’re allergic to penicillin, your options depend on the type of reaction you’ve had. People whose allergy caused a rash but not a severe anaphylactic reaction can typically take a first-generation cephalosporin like cephalexin (taken twice daily for 10 days) or cefadroxil (once daily for 10 days). These are closely related to penicillin but are generally safe for people with mild allergies. If your reaction to penicillin was severe, involving throat swelling, difficulty breathing, or a rapid drop in blood pressure, cephalosporins should be avoided.
For people who can’t take any penicillin-related drug, the main alternatives are:
- Azithromycin: A five-day course, making it the shortest option. It’s convenient, but resistance is a growing concern. Around one in three invasive Group A Strep infections now show resistance to this class of antibiotics, so it’s not the top backup choice.
- Clarithromycin: Taken twice daily for 10 days. It belongs to the same class as azithromycin and carries similar resistance concerns.
- Clindamycin: Taken three times daily for 10 days. It works through a different mechanism than the others and has shown particular usefulness in recurrent tonsillitis. In one study, patients treated with clindamycin for recurrent episodes had significantly fewer future flare-ups and were far less likely to need their tonsils removed. However, resistance to clindamycin has also been climbing, sometimes exceeding resistance rates for other alternatives, so local resistance patterns matter.
When Tonsillitis Keeps Coming Back
Recurrent bacterial tonsillitis sometimes responds poorly to penicillin, not because the strep bacteria are resistant, but because other bacteria in the throat can shield them from the antibiotic. In these situations, doctors may switch to clindamycin or a broader-spectrum cephalosporin that can address those co-existing bacteria. Second- and third-generation cephalosporins like cefuroxime and cefpodoxime have high efficacy rates, though their broader coverage means they carry a greater potential to disrupt your normal gut bacteria and contribute to resistance.
If someone experiences multiple confirmed strep infections in a single year, typically seven or more episodes in one year or five per year over two consecutive years, tonsillectomy becomes a conversation worth having with an ear, nose, and throat specialist.
What Happens Without Treatment
Viral tonsillitis resolves on its own. Bacterial tonsillitis caused by Group A Strep is a different story. Left untreated, it can trigger rheumatic fever, an inflammatory condition that affects the heart, joints, brain, and skin. If rheumatic fever itself goes untreated, it can progress to rheumatic heart disease, which damages the valves between the heart’s chambers and can require surgery or prove fatal.
Another potential complication is a peritonsillar abscess, a pocket of pus that forms beside the tonsil and can cause severe pain, difficulty swallowing, and a muffled voice. Kidney inflammation is a rarer but recognized complication as well. These risks are the core reason antibiotics are recommended for confirmed strep, even though the sore throat itself would eventually improve in most people without treatment.
What to Expect During Treatment
Once you start antibiotics, fever and the worst of the throat pain typically ease within two to three days. You’re generally considered no longer contagious after 24 hours on antibiotics, which is why schools and workplaces often use that as the return threshold. Full recovery of energy and appetite usually takes about a week.
During treatment, over-the-counter pain relievers, warm liquids, and cold foods like popsicles can help manage discomfort while the antibiotics do their work. If you’re three days into your course and symptoms haven’t improved at all, or if they’re getting worse, that’s worth a follow-up with your doctor, as it could signal a complication, an unusual bacterial cause, or a viral infection that antibiotics won’t touch.