A sore tonsil is almost always caused by an infection, and in most cases that infection is viral. Common cold viruses, influenza, and Epstein-Barr virus (the cause of mono) account for the majority of episodes. But the list of things that can make one or both tonsils hurt goes well beyond a simple cold: bacterial infections, tonsil stones, acid reflux, nerve conditions, and even structural abnormalities in nearby bone can all produce pain in or around the tonsils. Understanding which cause is behind your pain matters because some warrant nothing more than rest and fluids, while a few demand urgent medical attention.
Viral Infections Are the Most Common Culprit
If your tonsil hurts and you also have a runny nose, cough, or mild congestion, a virus is the most likely explanation. A study of children presenting with pharyngitis found that about 63% had at least one viral feature such as cough, runny nose, oral ulcers, or red eyes.1Pediatrics. Viral Features and Testing for Streptococcal Pharyngitis That pattern holds for adults too: the overwhelming majority of sore throats, including ones that feel concentrated in the tonsils, are caused by viruses that resolve on their own within a week or so. Pain relievers like ibuprofen or acetaminophen, warm liquids, and rest are usually all you need.
The worry people have, of course, is strep throat. Group A Streptococcus (GAS) is the main bacterial cause of tonsillitis, and it tends to come on fast with high fever, swollen and tender lymph nodes under the jaw, and white patches or pus on the tonsils, often without the cough and runny nose that point toward a virus. That said, the overlap between bacterial and viral symptoms is bigger than most people realize. A meta-analysis looking at the signs of GAS versus non-GAS pharyngitis concluded that no single sign or symptom reliably distinguishes one from the other.2PubMed. Signs and symptoms of Group A versus Non-Group A strep throat: A meta-analysis That is why a rapid strep test or throat culture matters when bacterial infection is suspected: you cannot diagnose strep by looking alone.3PubMed. Acute pharyngitis
How Doctors Decide Whether to Test or Treat
When you show up at a clinic with tonsil pain, your doctor is mentally running through a scoring system, even if they don’t mention it by name. The most widely used is the Centor score (sometimes called the modified McIsaac score), which assigns points for things like fever, tonsillar exudates, swollen anterior neck lymph nodes, and the absence of a cough. A higher score means a higher chance the infection is bacterial. Research in primary care found the score useful for triaging who should get a rapid strep test, though patients scoring a 3 out of 4 still need confirmation with a test rather than immediate antibiotics.4PubMed Central. Diagnostic Accuracy of Centor Score for Diagnosis of Group A Streptococcal Pharyngitis among Adults in Primary Care Clinics in Malaysia
A systematic review examining these scoring rules in secondary care found a real tradeoff: using a score of 3 or higher as a gateway to rapid testing reduced unnecessary antibiotic prescriptions significantly, but it also missed a substantial number of people who actually had strep. In a modeled population, restricting testing to higher scores cut antibiotic prescriptions nearly in half but left an estimated 893 true GAS cases untreated.5Clinical Microbiology and Infection. Systematic review and meta-analysis of the accuracy of McIsaac and Centor score in patients presenting to secondary care with pharyngitis None of this means you need to memorize the scoring criteria yourself. The practical takeaway is this: if your tonsil pain is severe, comes with high fever, and lacks cold-like symptoms, ask your doctor about a strep test rather than just waiting it out.
Peritonsillar Abscess
A peritonsillar abscess is what happens when a tonsil infection spreads into the tissue surrounding the tonsil and forms a pocket of pus. It typically shows up as severe, one-sided throat pain, difficulty opening the mouth (a sign called trismus), a muffled or “hot potato” voice, and drooling because swallowing becomes so painful. On examination, the soft palate bulges on the affected side and the uvula gets pushed away from it. A prospective study of 100 consecutive peritonsillar infection cases found that trismus, uvular deviation, and bulging of the anterior pillar were statistically associated with abscess rather than simple cellulitis.6Acta Otorrinolaringologica (English Edition). Peritonsillar Infections: Prospective Study of 100 Consecutive Cases
This is one of the “when to worry” scenarios. A peritonsillar abscess typically needs drainage, either by needle aspiration or a small incision, along with antibiotics. Left untreated, it can spread deeper into the neck, obstruct breathing, or, in rare cases, erode into a blood vessel. If your throat pain is dramatically worse on one side, you’re struggling to open your mouth, or you notice your voice changing, get to an emergency department.
Tonsil Stones
Tonsils are not smooth. They’re covered in deep pits and folds called crypts, and those crypts can collect dead cells, mucus, food debris, and bacteria. Over time, this material can calcify into small, pale, foul-smelling lumps known as tonsil stones (tonsilloliths). Most tonsil stones are tiny and cause nothing more than occasional bad breath or a vague foreign-body sensation in the throat.7Journal of the Scientific Society. A Giant Tonsillolith: An Unusual Cause for Longstanding Foreign Body Sensation in Throat But larger ones can press against the tonsil tissue and cause genuine discomfort, sometimes on one side only, sometimes with referred pain to the ear.
That ear pain connection is worth understanding. The tonsils share their nerve supply (the glossopharyngeal nerve) with part of the ear, so irritation in the tonsil area can produce pain that feels like it’s coming from inside the ear canal.8PubMed Central. Referred otalgia induced by a large tonsillolith If you have recurring ear pain that your doctor can’t find an ear-based cause for, tonsil stones are worth investigating. Small stones can often be dislodged at home with gentle pressure or gargling, though recurrent or large ones sometimes become a reason for tonsillectomy.
Acid Reflux That Reaches the Throat
Gastroesophageal reflux is widely recognized as a cause of heartburn, but when stomach acid travels far enough to reach the throat and voice box, it’s called laryngopharyngeal reflux (LPR). Unlike classic heartburn, LPR often doesn’t produce a burning sensation in the chest. Instead, people notice a chronic sore throat, throat clearing, a lump-in-the-throat feeling, or hoarseness. The tonsils sit right in the splash zone.
A 2025 study examined 112 adults with chronic tonsillitis and found that roughly 72% of them met diagnostic criteria for LPR. Among those who completed three months of anti-reflux treatment, about 64% reported complete relief from their sore throat, and average pain scores dropped significantly.9PubMed Central. Prevalence and clinical features of laryngopharyngeal reflux in adults with chronic tonsillitis The implication is striking: a meaningful fraction of people diagnosed with chronic tonsillitis may actually have reflux-driven throat irritation rather than a primary tonsil infection. If your tonsil pain is low-grade, persistent, and doesn’t come with fevers, reflux is worth considering, especially if you also have morning hoarseness or excessive throat clearing.
Chronic and Recurrent Tonsillitis
Some people get tonsillitis over and over again, with multiple episodes per year that may or may not respond fully to antibiotics. One reason infections recur is that bacteria in the tonsil crypts can form biofilms, which are structured communities of microorganisms encased in a protective matrix. Biofilms make bacteria far more resistant to antibiotics than free-floating bacteria would be.10PubMed Central. Chronic tonsillitis and biofilms: a brief overview of treatment modalities One study found biofilm evidence in 60% of surgically removed tonsils, and the presence of biofilms correlated with chronic infection symptoms rather than simple enlargement.11PubMed Central. Evidence of Bacterial Biofilms among Infected and Hypertrophied Tonsils in Correlation with the Microbiology, Histopathology, and Clinical Symptoms of Tonsillar Diseases
This is the biological explanation for why some people keep getting sick despite finishing every course of antibiotics: the antibiotics kill off the free-swimming bacteria and resolve the acute episode, but the biofilm remains as a reservoir that seeds the next flare-up. For adults stuck in this cycle, the question of tonsillectomy eventually comes up. Current guidelines typically look for a pattern of frequent, documented episodes (the classic “Paradise criteria” require seven episodes in one year, five per year for two years, or three per year for three years), though some research suggests those thresholds may be too restrictive for adults whose quality of life is heavily affected.12PubMed. Evaluation of Guidelines For Tonsillectomy in Adults With Recurrent Acute Tonsillitis
Allergies and Dry Air
Chronic allergic inflammation in the upper airway can cause the tonsils and adenoids to enlarge, a process sometimes called lymphoid hypertrophy.13PubMed. Pediatric allergic rhinitis and comorbid disorders Enlarged tonsils are more prone to trapping debris and getting irritated, which can produce a low-grade aching or soreness that waxes and wanes with allergy seasons. Many people attribute this discomfort to repeated infections when the underlying driver is actually allergic inflammation.
Dry air plays its own role. Mouth breathing, which is common in people with nasal congestion from allergies, exposes the throat to air that hasn’t been warmed and humidified by the nasal passages. Research has shown that breathing dry air through the mouth promotes inflammation by creating osmotic stress on the airway’s mucus lining, which activates pain-signaling neural pathways.14PubMed Central. Mouth breathing, dry air, and low water permeation promote inflammation, and activate neural pathways, by osmotic stresses acting on airway lining mucus If your tonsil pain is worst in the morning and improves as the day goes on, especially during dry winter months, the combination of mouth breathing and low humidity may be a contributing factor. A bedroom humidifier and treating the underlying nasal congestion can help more than throat lozenges.
Eagle Syndrome and Glossopharyngeal Neuralgia
Two less common conditions can produce pain that feels exactly like it’s coming from the tonsil, even though the tonsil itself is perfectly healthy. Eagle syndrome occurs when the styloid process, a small pointed bone at the base of the skull, is abnormally elongated or when the ligament connecting it to a bone in the throat becomes calcified. The elongated structure presses on nerves and soft tissue near the tonsil, causing dull, persistent pharyngeal pain, difficulty swallowing, and facial pain.15PubMed. The long styloid process syndrome or Eagle’s syndrome 16PubMed Central. Eagle syndrome The pain often worsens with turning the head or swallowing, and people sometimes go through years of being told they have tonsillitis before someone orders the CT scan that reveals the problem.
Glossopharyngeal neuralgia is a nerve condition that causes brief, severe, shock-like episodes of pain in the tonsil area, the base of the tongue, or the ear. The pain is intense enough to make people wince or cry out, but each episode usually lasts only seconds to a couple of minutes before vanishing completely.17PubMed Central. An uncommonly common: Glossopharyngeal neuralgia Swallowing, talking, coughing, or yawning can trigger an attack. It is rare, but if your tonsil pain comes in sudden, stabbing bursts rather than a constant ache, this diagnosis is worth raising with your doctor. Medications used for nerve pain (like carbamazepine) are often the first-line treatment.
When One Tonsil Stays Swollen
Asymmetry is something doctors take seriously. If one tonsil is persistently enlarged, hard, or ulcerated while the other looks normal, and this doesn’t resolve with a course of antibiotics, tonsillar cancer needs to be considered. Most tonsillar cancers are squamous cell carcinomas, and a growing proportion are linked to human papillomavirus (HPV). These cancers can present subtly: one-sided throat pain, a sensation of something stuck in the throat, an ear ache on the same side (due to the shared nerve supply mentioned earlier), or a painless lump in the neck.
Research on HPV-associated tonsillar squamous cell carcinoma has found that even when cancer appears to affect only one tonsil, there is a small but real chance of a synchronous tumor hiding in the opposite tonsil. In a study of patients who underwent bilateral tonsillectomy as part of their cancer workup, synchronous tumors in the contralateral tonsil were found in about 10% of cases overall, rising to 20% in patients deemed high-risk.18Laryngoscope Investigative Otolaryngology. Risk-Stratified Bilateral Tonsillectomy for Unilateral HPV-Associated Tonsillar SCC: Oncologic and Functional Outcomes From a Single Institution The point is not to alarm you: tonsillar cancer is uncommon, especially in younger people. But a unilateral tonsil that stays abnormal for weeks without explanation deserves imaging and possibly biopsy, not reassurance.
PFAPA in Children
If your child gets clockwork-like fevers every few weeks accompanied by sore throat, mouth sores, and swollen neck glands, and the episodes resolve completely between flares, a condition called PFAPA syndrome may be responsible. PFAPA stands for Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Adenitis, and it is the most common periodic fever syndrome in children, with most cases appearing before age five.19PubMed Central. Periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome: A review The distinguishing feature is the regularity: episodes arrive on a predictable schedule, sometimes so precise that parents can mark the calendar.
PFAPA is an autoinflammatory condition, meaning the immune system revs up without an actual infection. Children with PFAPA are completely well between episodes, which helps distinguish it from recurrent infections. Research examining tonsils removed from children with PFAPA found persistent localized inflammation in the tonsil tissue even when the child had no symptoms, and roughly 95% of patients in one cohort had complete resolution of episodes after tonsillectomy.20PubMed Central. Immune Dysregulation in the Tonsillar Microenvironment of Periodic Fever, Aphthous Stomatitis, Pharyngitis, Adenitis (PFAPA) Syndrome Recognizing the pattern matters because these children are often prescribed repeated courses of antibiotics for what looks like recurrent strep, when the treatment they actually need is different.
Autoimmune and Autoinflammatory Diseases
Beyond PFAPA, several systemic inflammatory conditions can produce tonsillar or pharyngeal pain as part of a broader symptom picture. Behçet’s disease, for instance, causes painful ulcers in the mouth and throat alongside genital ulcers and eye inflammation. Kawasaki disease in children can present with pharyngitis, cervical lymph node swelling, and changes in the oral mucosa. A systematic review of autoinflammatory diseases with head and neck manifestations highlighted both conditions as having characteristic pharyngeal involvement.21Acta Otorrinolaringologica (English Edition). Otorhinolaryngological manifestations of autoinflammatory diseases. Systematic review These causes are uncommon, but they’re worth knowing about because they tend to be missed if the doctor is only thinking about infection.
Lemierre’s Syndrome
This is the rarest entry on this list and the most dangerous. Lemierre’s syndrome occurs when a throat infection, usually caused by the bacterium Fusobacterium necrophorum, spreads to the internal jugular vein in the neck and causes an infected blood clot. From there, pieces of the infected clot can break off and travel to the lungs, joints, or other organs, seeding abscesses throughout the body.22PubMed Central. Some neck swellings are serious; a case of Lemierre’s Syndrome It’s a life-threatening condition that typically affects otherwise healthy young adults.23CMAJ. Lemierre syndrome: early recognition and management
The classic warning sign is a sore throat that seems to be improving, followed by a sudden worsening with high spiking fevers, rigors (whole-body shaking chills), neck swelling, and neck pain that extends beyond the throat. If someone who had a sore throat a few days ago develops these symptoms, they need emergency evaluation. Lemierre’s syndrome is extremely rare in the era of modern antibiotics, but it still occurs, and the key to survival is recognizing it early rather than dismissing worsening symptoms as just another viral illness.24PubMed Central. Lemierre’s syndrome: A persistent unusual neck pain and swelling
How Tonsils Change With Age
One thing many adults wonder is why their tonsils seem to bother them less as they get older. Tonsils are largest and most immunologically active during childhood, and they naturally shrink over time. But the changes go deeper than simple size reduction. Research examining tonsil tissue across a wide age range (3 to 85 years) found that the immune cell composition of the tonsil shifts substantially with age: granulocyte populations accumulate, and immune cells increasingly take on regulatory rather than inflammatory roles, potentially dampening the kind of exaggerated immune responses that drive symptomatic tonsillitis in children.25PubMed Central. Age-related changes of the innate immune system of the palatine tonsil in a healthy cohort This may partly explain why tonsillitis becomes less common in middle age, though it certainly doesn’t disappear entirely.
For older adults, a tonsil that hurts persistently or looks abnormal carries a different risk profile than the same complaint in a child. Infections are still possible, but malignancy becomes a more important consideration, and conditions like glossopharyngeal neuralgia are more likely to emerge in the fifth and sixth decades of life. Age alone doesn’t tell you what’s wrong, but it does shift the list of likely causes in ways your doctor should be accounting for.