Throat pain is most often caused by a viral infection, which accounts for 50% to 80% of all cases. Bacterial infections, allergies, acid reflux, and environmental irritants make up most of the rest. The cause matters because it determines whether you need treatment or just time.
Viral Infections Are the Most Common Cause
The common cold, flu, and other respiratory viruses are behind the majority of sore throats. These infections inflame the tissue lining the back of your throat (the pharynx), causing pain that typically worsens when you swallow. You’ll usually notice other symptoms alongside the throat pain: a runny nose, cough, sneezing, mild body aches, or a low-grade fever. Most viral sore throats resolve on their own within about a week.
Mononucleosis, caused by the Epstein-Barr virus, deserves a separate mention because the sore throat it produces can be severe and last much longer, sometimes two to four weeks. It often comes with extreme fatigue, swollen lymph nodes, and sometimes a swollen spleen. Mono is especially common in teenagers and young adults.
Strep and Other Bacterial Infections
Group A Streptococcus, the bacterium behind strep throat, causes 5% to 15% of sore throats in adults and 20% to 30% in children. Overall, bacteria account for roughly 20% to 50% of pharyngitis cases. Strep throat tends to come on suddenly with intense pain, fever, and swollen lymph nodes in the front of the neck. You might see white patches or streaks on the tonsils. Notably, cough and runny nose are usually absent, which is one of the clearest ways to distinguish strep from a viral sore throat.
Doctors use a simple scoring system to estimate how likely a sore throat is to be strep. It assigns one point each for: a history of fever, visible pus or coating on the tonsils, swollen tender lymph nodes at the front of the neck, and the absence of a cough. A score of zero or one means strep is unlikely and testing isn’t needed. A score of two or higher typically warrants a rapid strep test. Antibiotics shorten the illness and, more importantly, prevent rare but serious complications like rheumatic fever.
Acid Reflux That Reaches the Throat
Stomach acid doesn’t always stop at the esophagus. In a condition called laryngopharyngeal reflux (LPR), acid and a digestive enzyme called pepsin travel all the way up to the throat and voice box. The tissue there is far more delicate than the stomach lining, so even small amounts of acid can cause inflammation and damage. Pepsin breaks down proteins in the throat’s protective lining, weakening its barrier and triggering further irritation.
LPR feels different from classic heartburn. Instead of chest burning, you’re more likely to notice a persistent sore throat, a sensation of something stuck in your throat, frequent throat clearing, excess mucus, hoarseness, or a chronic cough. These symptoms tend to be worse during the day and while you’re upright, which is the opposite pattern of typical acid reflux that flares at night when you lie down. Because the symptoms overlap with so many other conditions, LPR often goes undiagnosed or gets mistaken for allergies or a lingering infection.
Allergies and Post-Nasal Drip
Allergic rhinitis, whether from pollen, dust mites, pet dander, or mold, can produce a sore throat even though the allergy itself targets your nose and sinuses. When your nasal passages produce excess mucus, it drains down the back of your throat. Researchers originally assumed this drainage directly irritated the throat through mechanical or chemical stimulation, though more recent studies suggest the relationship is more complex. Regardless of the exact mechanism, the result is the same: a raw, scratchy throat that tends to be worse in the morning after a night of mucus draining while you slept.
If your sore throat follows a seasonal pattern, gets worse outdoors, or comes with itchy eyes and sneezing, allergies are a likely culprit. Unlike infections, allergy-related throat pain won’t cause a fever or swollen lymph nodes.
Dry Air and Environmental Irritants
Breathing dry air, especially overnight with your mouth open, strips moisture from your throat lining and leaves it irritated by morning. Population-based research has shown that both cold temperatures and low humidity independently increase the risk of sore throat. Indoor air that isn’t humidified is linked to higher rates of irritation symptoms overall, which is why sore throats spike in winter when heating systems dry out indoor air.
Other environmental triggers include cigarette smoke (firsthand or secondhand), air pollution, chemical fumes, and dust. These irritants cause direct inflammation of the throat tissue. The pattern is the giveaway: if your throat feels better when you leave a particular environment and worse when you return, something in that space is likely the cause.
Muscle Strain and Overuse
Your throat contains muscles that can get sore from overuse, just like any other muscle. Yelling at a concert, speaking loudly for hours, or singing without proper technique can leave your throat aching. The pain usually centers around the voice box area and comes with hoarseness. It resolves with rest, hydration, and a day or two of speaking as little as possible.
Less Common but Serious Causes
A peritonsillar abscess forms when a bacterial infection spreads beyond the tonsil into the surrounding tissue, creating a pocket of pus. The pain is severe and usually one-sided. You may have difficulty opening your mouth fully, notice your voice sounds muffled or “hot potato”-like, or find yourself drooling because swallowing is too painful. This requires urgent medical drainage.
Epiglottitis, an infection of the small flap of cartilage that covers your windpipe, is rare in adults but dangerous. It causes rapidly worsening throat pain, difficulty swallowing, drooling, and sometimes a high-pitched sound when breathing in. It can obstruct the airway and is a medical emergency.
Throat cancers can cause persistent pain that doesn’t resolve, particularly if you’re a smoker, heavy drinker, or have been exposed to HPV. A sore throat lasting more than two weeks without an obvious explanation, especially if paired with ear pain on one side, difficulty swallowing, unexplained weight loss, or a lump in the neck, warrants evaluation.
How to Tell What’s Causing Yours
The timeline and accompanying symptoms are your best clues. A sore throat that arrives with a stuffy nose, cough, and mild fatigue is almost certainly viral and will clear up within a week. One that hits suddenly with high fever, no cough, and swollen neck glands points toward strep and is worth testing for. Throat pain that lingers for weeks without other cold symptoms, particularly with hoarseness or a lump-in-the-throat feeling, suggests reflux, allergies, or something that needs a closer look.
Pay attention to patterns. Morning-only soreness that improves as the day goes on often points to dry air or nighttime mouth breathing. Pain that worsens after meals or when lying down suggests reflux. Seasonal flares with itchy eyes suggest allergies. A sore throat that doesn’t improve after two weeks, or one accompanied by difficulty breathing, inability to swallow liquids, or a muffled voice, needs prompt medical attention.