Strep throat is a bacterial infection of the throat and tonsils caused by group A Streptococcus bacteria. It accounts for roughly 20 to 30 percent of sore throats in children and 5 to 15 percent in adults, making it one of the most common reasons people visit a doctor for throat pain. Unlike most sore throats, which are caused by viruses and clear up on their own, strep throat requires antibiotics to heal properly and prevent complications.
How Strep Throat Feels
The hallmark of strep throat is a sudden, severe sore throat that comes on fast. Swallowing feels painful, and the back of the throat often looks red with swollen tonsils, sometimes dotted with white patches or streaks of pus. You may also notice tiny red spots on the roof of your mouth. A fever of 101°F (38.3°C) or higher is common, and the lymph nodes at the front of your neck often swell and feel tender to the touch.
What’s just as useful as knowing the symptoms of strep is knowing what strep typically does not cause. If you have a cough, runny nose, hoarseness, or pink eye alongside your sore throat, a virus is the more likely culprit. Strep throat tends to affect the throat in isolation, without the upper respiratory symptoms that come with a cold or flu. Children may also experience headaches, stomachaches, nausea, or vomiting, which can make strep tricky to identify in younger kids who can’t describe their throat pain clearly.
How It Spreads
Group A Strep bacteria travel through respiratory droplets. Coughing, sneezing, or even talking at close range can pass the bacteria from one person to another. Sharing cups, utensils, or food with someone who’s infected is another common route. The bacteria can also live briefly on surfaces, so washing dishes and cups used by a sick person matters.
Without treatment, a person with strep throat can remain contagious for weeks. With antibiotics, that window shrinks dramatically. After 24 hours on antibiotics and with no fever, most people are no longer contagious and can return to work, school, or daycare.
How It’s Diagnosed
A doctor can’t diagnose strep throat just by looking at your throat. The symptoms overlap too much with viral infections. Instead, diagnosis requires a test. The most common is a rapid strep test, where a swab of the back of your throat gives results in minutes. If that test comes back negative but strep is still suspected (especially in children), a throat culture may be sent to a lab, which takes one to two days but is more accurate.
Adults with classic cold symptoms like cough and congestion generally don’t need testing, since those signs point strongly toward a virus. Testing is most useful when you have throat pain, fever, swollen lymph nodes, and tonsillar swelling without the typical cold symptoms.
Treatment and Recovery
Antibiotics are the standard treatment for strep throat. Penicillin and amoxicillin are the first-choice options, and the typical course lasts 10 days. It’s important to finish the entire course even after you start feeling better, which usually happens within a day or two. Stopping early can allow surviving bacteria to rebound and increases the risk of complications.
If you’re allergic to penicillin, several alternatives are available. Your doctor will choose one based on your specific allergy history, but effective options exist across multiple antibiotic classes. Most people notice significant improvement within 48 hours of starting treatment. In the meantime, over-the-counter pain relievers, warm liquids, and throat lozenges can help manage discomfort.
Why Treatment Matters: Potential Complications
Strep throat on its own is uncomfortable but not dangerous. The reason antibiotics are so strongly recommended is to prevent rare but serious complications that can develop if the infection goes untreated. The two most concerning are rheumatic fever and a kidney condition called post-streptococcal glomerulonephritis (PSGN).
Rheumatic fever is an inflammatory condition that can damage the heart valves, cause joint pain, and affect the nervous system. It typically develops two to four weeks after an untreated strep infection. It’s rare in the United States today, largely because of routine antibiotic treatment, but it remains a significant problem in parts of the world with limited healthcare access.
PSGN is a kidney inflammation that can develop about 10 days after strep throat symptoms begin. Signs include dark, reddish-brown urine, swelling (particularly around the eyes, hands, and feet), decreased urine output, fatigue, and high blood pressure. Some people have symptoms so mild they don’t notice them. Most cases of PSGN resolve on their own, but the condition sometimes requires medical management to control blood pressure and swelling.
Other possible complications include peritonsillar abscesses (a pocket of pus near the tonsils), sinus infections, and ear infections. These are less common but can develop if the bacteria spread to nearby tissues.
Strep Throat in Children vs. Adults
Strep throat is most common in children between ages 5 and 15. Kids in school and daycare settings are especially vulnerable because of close contact and shared spaces. Children are also more likely to develop rheumatic fever from untreated strep, which is one reason pediatricians test for it frequently.
Adults do get strep throat, but less often. Parents of school-age children and adults who work closely with kids have higher exposure. In adults over 45, strep throat becomes increasingly uncommon, and other causes of severe sore throat (including some that need different treatment) become more relevant.
Preventing Strep Throat
There’s no vaccine for group A Strep, and you can get strep throat more than once. Prevention comes down to practical hygiene. Wash your hands frequently with soap and water, especially after coughing or sneezing and before eating. Avoid sharing cups, utensils, or bites of food with anyone who’s sick. Cover coughs and sneezes with your elbow rather than your hand.
If someone in your household has strep, wash their dishes and utensils separately or run them through the dishwasher. Replacing your toothbrush after you’ve been on antibiotics for a couple of days is a commonly recommended precaution, since bacteria can linger on bristles. Keeping sick family members’ personal items separate during the contagious period, particularly in the first 24 hours of antibiotic treatment, helps reduce household spread.