Penicillin and amoxicillin are the first-line antibiotics for strep throat. They’ve been the standard treatment for decades because group A strep bacteria have never developed resistance to them. Most courses last 10 days, though you’ll start feeling better well before that. If you’re allergic to penicillin, several effective alternatives exist.
Penicillin and Amoxicillin: The Go-To Options
Penicillin V (the oral tablet form) and amoxicillin are equally effective at clearing a strep infection. Amoxicillin is prescribed more often for children because it comes in a chewable tablet and a flavored liquid suspension, both of which are easier for kids to take than swallowing a pill. Amoxicillin also has the advantage of once- or twice-daily dosing for strep, while penicillin V is typically taken two to three times a day.
Both are taken for a full 10 days. This is true even though your symptoms will likely improve significantly within two to three days. The full course is necessary to completely eliminate the bacteria from your throat, which reduces the chance of a relapse and helps prevent complications like rheumatic fever, a serious inflammatory condition that can develop one to five weeks after an untreated strep infection.
Alternatives if You’re Allergic to Penicillin
A penicillin allergy doesn’t limit your options as much as you might think. The CDC lists several alternatives, and the right one depends on the type of allergic reaction you’ve had.
If your allergy caused a rash but not a severe reaction (like throat swelling or difficulty breathing), certain cephalosporin antibiotics are safe options. Cephalexin, taken twice daily for 10 days, and cefadroxil, taken once daily for 10 days, are both recommended. These are chemically related to penicillin but are well tolerated by most people whose penicillin allergy is mild. However, if you’ve ever had a severe, immediate allergic reaction to penicillin, cephalosporins should be avoided.
For people with a severe penicillin allergy, the main options are:
- Azithromycin: A 5-day course, starting with a larger dose on day one followed by a smaller daily dose for four more days. This is the shortest strep treatment available.
- Clarithromycin: Taken twice daily for 10 days.
- Clindamycin: Taken three times daily for 10 days.
Azithromycin (commonly known by the brand name Z-Pack) is popular because of its short course and once-daily dosing, but it’s not a first choice for strep when penicillin is an option. Some strep strains have developed resistance to it, making it less reliable than penicillin or amoxicillin.
Why 10 Days Matters
The 10-day course is one of the longest antibiotic regimens people encounter for a common infection, and it’s the part most people struggle with. By day three or four, your throat feels fine, your fever is gone, and taking pills for another week feels pointless. But the bacteria that cause strep throat are embedded in throat tissue, and shorter courses leave behind enough survivors to cause a rebound infection or allow you to spread it to others.
There’s also the issue of rheumatic fever. This complication is rare in the United States, but it still occurs, and it’s almost entirely preventable with a completed antibiotic course. Rheumatic fever can damage heart valves permanently. Adequate treatment of strep throat is the primary way to prevent it, according to the CDC.
How Quickly Antibiotics Work
You should notice your symptoms improving within the first two to three days of starting treatment. Fever typically breaks within 24 hours. Throat pain gradually eases over the next day or two, though mild soreness can linger a bit longer.
From a contagion standpoint, you stop being infectious about 12 hours after your first dose. That’s the benchmark schools and daycares use for readmission: children can return 12 hours after starting antibiotics, as long as they feel well enough. Without antibiotics, strep remains contagious for two to three weeks.
Treating Strep in Children
Amoxicillin is the standard choice for kids. It’s available as a powder mixed into a liquid suspension, which makes dosing easy for young children who can’t swallow tablets. Older children can use chewable tablets instead. The dose is calculated based on body weight, so your child’s prescription will be specific to them.
Infants three months and younger have immature kidney function, which affects how their bodies process the drug, so dosing adjustments are necessary in that age group. For most children beyond that age, amoxicillin is well studied and straightforward.
The biggest challenge with kids is compliance. A 10-day course is a long time to remember a twice-daily medication for a child who feels fine by day three. Setting a daily alarm or tying the dose to a consistent routine (like breakfast and bedtime) helps. If your child truly can’t tolerate a 10-day regimen, azithromycin’s 5-day course is sometimes used as an alternative, though it’s less effective against resistant strains.
What Happens Without Antibiotics
Strep throat will eventually resolve on its own in most cases. The sore throat and fever typically clear within a week even without treatment. But “getting better” isn’t the same as “safe to skip antibiotics.” Untreated strep carries the risk of complications that treated strep almost never causes.
Rheumatic fever is the most serious concern, but not the only one. Untreated strep can also lead to peritonsillar abscesses (painful pockets of pus behind the tonsils), kidney inflammation, and spread of infection to the sinuses or ears. Antibiotics shorten the illness, reduce contagiousness, and prevent these outcomes. The risk-to-benefit calculation strongly favors treatment.