Most sore throats are caused by viral infections, the same ones responsible for the common cold and flu. Viruses account for the vast majority of cases, while bacteria like strep cause only 10 to 20% of sore throats. But infections aren’t the only culprit. Acid reflux, dry air, smoking, and even sexually transmitted infections can all make your throat hurt.
Why a Sore Throat Hurts
When something irritates or infects the lining of your throat, your immune system responds with inflammation. Damaged cells release chemical signals, primarily prostaglandins and bradykinin, that activate pain receptors in the throat tissue. Prostaglandins lower your pain threshold so that even normal swallowing feels sharp and raw. Bradykinin directly triggers nerve endings. Together, they create the familiar burning, scratchy, or stabbing sensation that makes every swallow noticeable.
This pain mechanism is the same regardless of whether the cause is a virus, bacteria, stomach acid, or dry air. The trigger differs, but the inflammatory response in the throat tissue follows the same pathway.
Viral Infections: The Most Common Cause
The viruses behind most sore throats are ones you already know: rhinoviruses (the common cold), influenza, coronaviruses, adenoviruses, and parainfluenza viruses. Rhinoviruses alone cause a huge share of cases, partly because nasal secretions drip down the back of the throat and irritate the tissue directly.
A viral sore throat typically comes with other symptoms: a cough, runny nose, headache, or sometimes a rash. You might also notice red, watery eyes if an adenovirus is involved. These infections usually resolve on their own within a week, and antibiotics do nothing against them.
One viral cause worth knowing about separately is the Epstein-Barr virus, which causes mononucleosis. Mono produces a severe sore throat, often with white patches on swollen tonsils, along with deep fatigue, muscle aches, and swollen lymph nodes on both the front and back of the neck. The acute illness typically clears in about two weeks, but the fatigue and swollen glands can linger for months.
Strep Throat and Other Bacterial Causes
Group A Streptococcus is the bacterial cause people worry about most, and for good reason: untreated strep can, in rare cases, lead to complications like rheumatic fever. But strep accounts for only about 10 to 20% of sore throat cases overall. It tends to come on suddenly, with intense throat pain, fever, and swollen lymph nodes but typically without a cough or runny nose. That absence of cold symptoms is one of the distinguishing features.
Despite the relatively low prevalence of bacterial sore throats, antibiotics are prescribed far more often than they should be. One large study of primary care visits found that 66% of sore throat appointments resulted in an antibiotic prescription, with the rate climbing to 75% for children under five. Current guidelines recommend antibiotics only for confirmed strep cases, people at high risk for rheumatic fever, or those with very severe symptoms like difficulty swallowing. The overprescription contributes to antibiotic resistance without helping patients whose sore throats are viral.
Acid Reflux and Throat Irritation
If your sore throat is chronic or keeps coming back without any obvious infection, acid reflux may be the cause. When stomach contents flow backward into the esophagus and reach the throat, the acid and a digestive enzyme called pepsin damage the delicate lining of the larynx and pharynx. Your throat tissue is far more vulnerable to acid than your esophagus. Research shows the esophagus can handle roughly 50 reflux episodes per day without injury, while the throat lining starts sustaining damage after just four.
Pepsin is especially destructive. Once it reaches throat tissue, it breaks down proteins and disrupts the protective barrier between cells, triggering inflammation even at relatively mild acid levels. People with this condition, known as laryngopharyngeal reflux, often describe a persistent sore or dry throat, frequent throat clearing, and a sensation of something stuck in the throat. Unlike typical heartburn, many people with throat reflux don’t feel the classic chest burn at all, which makes it easy to overlook.
Dry Air and Environmental Irritants
Breathing dry air, especially during winter when indoor heating strips moisture from the air, can irritate your throat all on its own. When humidity drops to very low levels (around 10%), the mucus layer coating your airways dries out and loses its ability to trap particles and keep tissue hydrated. Research modeling airway conditions found that dry air promotes inflammation and activates pain-signaling pathways through osmotic stress on the airway lining. The mucus becomes concentrated, triggering the release of inflammatory molecules in the same way an infection would.
Mouth breathing makes this worse. If you sleep with your mouth open, especially with a stuffy nose, you bypass the nasal passages that normally warm and humidify incoming air. The result is a raw, scratchy throat that’s worst in the morning and gradually improves as you drink fluids throughout the day. Cigarette smoke, air pollution, and chemical fumes are also common throat irritants that cause chronic, low-grade inflammation of the pharynx.
Sexually Transmitted Infections
Sore throats caused by STIs are more common than many people realize, and they’re easy to miss. Gonorrhea can infect the throat through oral sex, producing a sore, dry throat, though most people with pharyngeal gonorrhea have no symptoms at all. Chlamydia can also affect the throat in a similar way. Because these infections are so often silent, they can go undiagnosed and untreated for long periods. If you have a persistent sore throat with no obvious cause and recent oral sexual contact, an STI screen is worth considering.
When a Sore Throat Signals Something Serious
The vast majority of sore throats are harmless and resolve within days. But a small number point to a condition that needs immediate attention. Epiglottitis, an inflammation of the flap that covers the windpipe during swallowing, is a medical emergency. The warning signs include difficulty breathing, drooling because swallowing has become too painful or difficult, a muffled or hoarse voice, and a high-pitched whistling sound when breathing in (called stridor). These symptoms can develop quickly in both children and adults, and they require emergency care because the swelling can block the airway.
A sore throat that lasts longer than two weeks, occurs alongside a lump in the neck, or comes with unexplained weight loss also warrants a closer look. These aren’t typical of infections and may point to conditions that benefit from early evaluation.