A sore throat is most often a symptom of a viral infection, such as a cold, the flu, or COVID-19. Viruses account for 85% to 95% of sore throats in adults. But a sore throat can also signal a bacterial infection, acid reflux, allergies, or simple environmental irritation, and telling the difference matters because some causes need treatment while others resolve on their own.
Common Cold, Flu, and COVID-19
The three most common viral culprits all produce a sore throat, but they tend to come packaged with different sets of symptoms. A cold (usually caused by rhinovirus) typically brings a runny or stuffy nose, sneezing, and mild fatigue, with the sore throat appearing early and fading within a few days. The flu hits harder: expect a sudden onset of fever, body aches, chills, and exhaustion alongside the throat pain. COVID-19 overlaps with both but is more likely to include loss of taste or smell, shortness of breath, or a dry cough.
In all three cases, the sore throat is your immune system reacting to the virus in the tissues lining your throat. It usually peaks in the first two to three days and improves on its own. Staying hydrated, using throat lozenges, and resting are the main things you can do. Antibiotics don’t work against viruses, so they won’t help here.
Strep Throat and Other Bacterial Infections
Only about 10% of adult sore throats are caused by bacteria, most commonly group A strep. Strep throat feels different from a viral sore throat in a few important ways. Doctors look for four signs that raise suspicion: a fever of 100.4°F (38°C) or higher, swollen lymph nodes at the front of your neck, white patches or swelling on the tonsils, and the absence of a cough. The more of these you have, the more likely the cause is bacterial rather than viral. A cough actually makes strep less likely, because it points toward a virus instead.
If your doctor suspects strep, you’ll typically get a rapid strep test, a throat swab that returns results in minutes. These tests correctly identify strep about 79% of the time, so a negative result with strong symptoms may prompt a follow-up throat culture, which takes a day or two but is more accurate.
Treating strep matters because untreated infections can lead to rheumatic fever, an inflammatory condition that can damage heart valves, affect joints, and in severe cases require surgery. Rheumatic fever is rare, but it’s entirely preventable with a course of antibiotics.
Mono (Epstein-Barr Virus)
Infectious mononucleosis, or mono, causes a particularly severe and long-lasting sore throat. It’s caused by the Epstein-Barr virus and is most common in teenagers and young adults. The throat pain is often intense enough to make swallowing difficult, and you may notice swollen lymph nodes in the neck, significant fatigue, fever, and sometimes a rash.
Most people recover in two to four weeks, but the fatigue can linger for several weeks or even months. The spleen can also become enlarged during mono, which is why doctors recommend avoiding contact sports and heavy lifting until you’ve fully recovered. There’s no antiviral treatment for mono. Recovery depends on rest, fluids, and time.
Acid Reflux That Reaches Your Throat
A sore throat that keeps coming back without any signs of infection may be caused by acid reflux, specifically a form called laryngopharyngeal reflux (LPR). In this condition, stomach acid travels all the way up into the throat, irritating the tissues there. What makes LPR tricky is that many people with it never experience the classic heartburn you’d associate with reflux. That’s why it’s sometimes called “silent reflux.”
Along with throat soreness, LPR can cause a feeling of something stuck in your throat, chronic throat clearing, hoarseness, and postnasal drip. The symptoms tend to be worse in the morning or after meals. Smoking, alcohol, caffeine, and spicy or acidic foods all make it worse because they relax the muscle at the top of the esophagus that normally keeps acid from reaching the throat. Cutting back on those triggers, eating smaller meals, and not lying down within a few hours of eating can make a noticeable difference.
Allergies and Postnasal Drip
Seasonal or year-round allergies can produce a sore throat even though no infection is present. The mechanism is indirect: allergens like pollen, dust mites, or pet dander trigger excess mucus production in the sinuses. That mucus drips down the back of the throat (postnasal drip), irritating the tissue and creating a raw, scratchy feeling. The soreness tends to be worse in the morning after mucus has accumulated overnight.
The giveaway that allergies are the cause is the company the sore throat keeps. If you also have itchy or watery eyes, sneezing, and a clear runny nose but no fever or body aches, allergies are a more likely explanation than an infection. Treating the underlying allergy with antihistamines or nasal sprays usually resolves the throat irritation.
Environmental and Lifestyle Irritants
Sometimes a sore throat isn’t caused by an illness at all. Dry indoor air, especially in winter when heating systems run constantly, pulls moisture from the tissues in your throat and leaves them irritated. Breathing through your mouth while sleeping has the same effect. Smoke exposure, whether from cigarettes or wildfire smoke, directly irritates the throat and vocal cords. Even heavy voice use, like shouting at a concert or talking all day for work, can leave your throat raw and inflamed.
These causes are usually easy to identify because the soreness lines up with the exposure. A humidifier, staying hydrated, and removing the irritant typically resolve the problem within a day or two.
When a Sore Throat Needs Urgent Attention
Most sore throats are uncomfortable but harmless. A few warning signs, however, suggest something more serious is going on. Difficulty breathing or difficulty swallowing (not just pain with swallowing, but an actual inability to swallow) require emergency medical care. A muffled or “hot potato” voice, drooling because you can’t manage your saliva, or a sore throat with a very high fever and no other cold symptoms also warrant prompt evaluation. These can indicate a peritonsillar abscess or swelling severe enough to compromise your airway.
A sore throat that persists beyond two weeks without improvement, especially in someone who smokes or drinks heavily, is worth getting checked out. Persistent hoarseness or a lump-like sensation that doesn’t resolve could point to conditions that benefit from early detection.