Strep throat is a bacterial infection that causes a sudden, severe sore throat along with red, swollen tonsils that often have white patches or streaks of pus. Unlike a regular sore throat from a cold, strep comes on fast, hits hard, and needs antibiotics to clear up safely. Most cases last three to five days with treatment.
What Strep Throat Looks and Feels Like
The hallmark of strep throat is a sore throat that appears suddenly, not one that builds gradually over a day or two. Your tonsils become red and swollen, and you may notice white patches or streaks of pus on them. Another telltale sign is tiny red spots on the roof of your mouth, called petechiae. Your lymph nodes along the front of your neck will often feel swollen and tender.
Fever is common, and many people also experience headache, stomach pain, or nausea, particularly children. What strep throat typically does not cause is equally important: if you have a runny nose, cough, hoarseness, or pink eye, the culprit is more likely a virus than strep. That distinction is one of the key things doctors use to decide whether to test you.
What Causes It
Strep throat is caused by a bacterium called group A Streptococcus. It spreads through respiratory droplets when an infected person coughs, sneezes, or talks, and through shared food or drinks. The bacteria colonize the tissue at the back of your throat and on your tonsils, triggering the immune response that produces the swelling, redness, and pain you feel.
Interestingly, between 5 and 15% of children carry group A strep in their throats at any given time without showing symptoms. These carriers can test positive on a throat swab even though they don’t have an active infection, which is one reason doctors generally won’t test you unless symptoms point toward strep.
How It’s Diagnosed
Doctors use a set of clinical clues to decide whether strep is likely before running a test. The criteria they weigh include your age, whether you have a fever, swollen lymph nodes in the front of your neck, pus on your tonsils, and whether you have a cough (the absence of a cough makes strep more likely). If the picture fits, you’ll get a rapid strep test, which involves a quick throat swab and returns results in minutes. A throat culture, which takes a day or two, is sometimes used as a backup if the rapid test is negative but suspicion remains high.
How Strep Throat Is Treated
Antibiotics are the standard treatment. Penicillin and amoxicillin are the first choices, and the typical course lasts 10 days. It’s important to finish the full course even though you’ll start feeling better much sooner. If you have a penicillin allergy, several alternatives are available, so let your doctor know upfront.
Most people notice improvement within a day or two of starting antibiotics. You become much less contagious within 24 to 48 hours of your first dose. The general rule is that once you’ve been on antibiotics for at least 24 hours and your fever has broken, you can return to work, school, or daycare without worrying about spreading it to others. Without antibiotics, you remain contagious for longer and face a higher risk of complications.
What Happens if Strep Goes Untreated
Most of the time, the sore throat itself would eventually resolve on its own. The real danger of skipping treatment is what can happen afterward. The most serious complication is rheumatic fever, an inflammatory condition that can damage the heart, joints, brain, and skin. Rheumatic fever develops when the body’s immune response to the strep bacteria misfires and begins attacking its own tissues.
If rheumatic fever goes untreated, it can progress to rheumatic heart disease, which weakens the valves between the chambers of the heart. Severe cases can require heart surgery and can be fatal. Symptoms of rheumatic fever include chest pain, a fast heartbeat, shortness of breath, new heart murmurs, and joint pain. Another possible complication is a kidney condition called post-streptococcal glomerulonephritis, where the immune response damages the kidneys’ filtering units.
These complications are uncommon in places where antibiotics are readily available, but they are the reason strep throat is treated with a full 10-day course rather than just managing symptoms until you feel better. The antibiotics aren’t only clearing the infection. They’re preventing the immune overreaction that causes lasting damage.
Strep Throat vs. a Viral Sore Throat
The overlap in symptoms between strep and a garden-variety viral sore throat is why testing matters. A few patterns can help you tell them apart before you even get to a clinic:
- Speed of onset: Strep tends to hit suddenly. A viral sore throat usually creeps in alongside other cold symptoms.
- Cough and congestion: If you’re coughing, sneezing, or dealing with a runny nose, it’s more likely viral. Strep rarely causes those symptoms.
- White patches on tonsils: Common with strep, less so with most viral infections.
- Fever: Strep often produces a higher fever. Many viral sore throats come with a low-grade fever or none at all.
- Age: Strep is most common in children between 5 and 15. It’s less common in adults and rare in children under 3.
None of these signs are definitive on their own. A throat swab is the only way to confirm strep, and knowing for certain matters because antibiotics won’t help a viral infection but are essential for a bacterial one.