Most sore throats are caused by viral infections. Viruses account for 50% to 80% of all cases, while bacteria cause roughly 20% to 50%. The remaining cases come from non-infectious sources like allergies, acid reflux, and environmental irritants. Understanding the cause matters because it determines whether you need antibiotics or just time and rest.
Viral Infections: The Most Common Cause
The common cold is the single biggest driver of sore throats. Rhinoviruses and other cold viruses inflame the tissue lining your throat, making it feel raw, scratchy, or painful when you swallow. But colds are far from the only viral culprit. The flu, COVID-19, mono (Epstein-Barr virus), measles, chickenpox, and croup in children all produce sore throats as a primary or early symptom.
Viral sore throats typically come packaged with other symptoms: a runny nose, cough, sneezing, watery eyes, or a hoarse voice. That cluster of symptoms is actually a useful clue. If you have a sore throat plus a cough and nasal congestion, a virus is almost certainly the cause. Most viral sore throats resolve on their own within three to ten days without any specific treatment.
Strep Throat and Other Bacterial Infections
Group A Streptococcus is the most common bacterial cause of sore throat, responsible for 20% to 30% of cases in children and 5% to 15% in adults. Strep throat feels different from a viral sore throat. It tends to come on suddenly, with intense pain when swallowing and a fever. You might also notice swollen lymph nodes at the front of your neck, red spots on the roof of your mouth, or white patches on your tonsils.
Children with strep sometimes have symptoms that seem unrelated to the throat: stomach pain, headache, nausea, or vomiting. In some cases, strep produces a rough, sandpaper-like rash across the body, a condition called scarlet fever.
One of the most reliable ways to tell strep apart from a virus is what you don’t have. People with strep throat typically don’t have a cough, runny nose, hoarseness, mouth sores, or pink eye. If your sore throat came with a cough and congestion, strep is unlikely. Doctors use a scoring system based on your age, whether you have a fever, swollen lymph nodes, tonsillar coating, and the presence or absence of a cough to decide whether a strep test is warranted. A high score on that checklist means testing, and potentially antibiotics, is appropriate. A low score usually means antibiotics won’t help.
When strep is confirmed and treated with antibiotics, most people take a ten-day course. Without treatment, strep can occasionally lead to complications affecting the heart or kidneys, which is why getting tested matters when the symptoms fit.
Allergies, Reflux, and Environmental Irritants
Not every sore throat comes from an infection. Allergies to pollen, mold, dust, or pet dander can cause postnasal drip, where mucus drains down the back of your throat and irritates it over hours or days. This type of sore throat tends to be worse in the morning and improves as the day goes on, or it flares seasonally when allergen counts are high.
Acid reflux is another common non-infectious cause. When stomach acid travels up into the esophagus or all the way into the throat (a condition called laryngopharyngeal reflux), it can produce a persistent sore, burning sensation. People with reflux-related throat pain often don’t have the classic heartburn feeling, which makes it easy to overlook as the source. Clues include a sore throat that lingers for weeks, a feeling of a lump in the throat, or a voice that sounds rougher than usual, especially in the morning.
Breathing dry indoor air, particularly during winter months with heating running, dries out the throat lining and can cause soreness. Exposure to cigarette smoke, air pollution, or chemical fumes does the same. These triggers tend to cause chronic or recurring throat irritation rather than the acute, intense pain of an infection.
Rare but Serious Causes
A small number of sore throats signal something more dangerous. Epiglottitis is an inflammation of the small flap of tissue that covers your windpipe during swallowing. It’s rare, affecting roughly 1 to 4 out of every 100,000 adults in the U.S., but it can become life-threatening if the swelling blocks the airway. Symptoms go beyond a typical sore throat: difficulty breathing, drooling, a high-pitched whistling sound when inhaling, a muffled or abnormal voice, and a high fever. Young children with epiglottitis often sit leaning forward with their mouth open, visibly struggling to breathe. This requires emergency care.
A peritonsillar abscess, where a pocket of pus forms near the tonsils, is another serious possibility. It usually develops as a complication of untreated or undertreated tonsillitis. The pain is typically severe and one-sided, and opening the mouth becomes difficult. Like epiglottitis, this needs prompt medical treatment, usually drainage and antibiotics.
How to Tell What’s Causing Yours
The pattern of your symptoms is the best first clue. A sore throat with a cough, runny nose, and sneezing points strongly to a virus. A sore throat with sudden onset, fever, swollen neck glands, and no cough points toward strep. A sore throat that lingers for weeks without other cold symptoms suggests an environmental or reflux-related cause.
Timing helps too. Viral sore throats peak within the first few days and gradually improve over a week or so. If your sore throat hasn’t improved after ten days, keeps coming back, or gets dramatically worse rather than gradually better, the cause is likely something beyond a simple cold virus. Difficulty breathing, inability to swallow liquids, drooling, or a fever above 101°F with no cold symptoms are signs that warrant a same-day medical evaluation rather than watchful waiting.