Why Does My Left Tonsil Hurt? Causes & When to See a Doctor

One-sided tonsil pain, whether left or right, almost always traces to the same short list of causes that affect both tonsils, just hitting one side harder. The most common explanation is a garden-variety throat infection that happens to flare more in one tonsil than the other, but peritonsillar abscesses, tonsil stones, nerve disorders, and structural abnormalities can all produce pain that stays stubbornly on one side. While unilateral tonsil pain is rarely dangerous on its own, certain accompanying symptoms change the picture considerably.

Infections That Hit One Side Harder

A standard bout of tonsillitis or pharyngitis can feel worse on one side even when both tonsils are technically inflamed. The two palatine tonsils are separate structures with their own blood supply and crypt architecture, so bacteria or viruses don’t always colonize them evenly. You might notice the left tonsil looking redder, more swollen, or more painful than the right, and this is completely normal during an otherwise routine infection. Viral sore throats caused by common cold viruses, influenza, or Epstein-Barr virus (the mono culprit) can all produce asymmetric symptoms. Bacterial infections, especially from Group A Streptococcus, also tend to favor one side at times.

What matters clinically is less which side hurts and more how long it hurts and what else is happening. A sore throat from a viral infection typically resolves within a week. Strep throat usually responds to antibiotics within a day or two. If your left tonsil has been sore for more than about ten days, or the pain keeps getting worse rather than plateauing, the cause may not be a straightforward infection.

Peritonsillar Abscess

A peritonsillar abscess is the most common deep infection of the head and neck, and it almost always affects just one side. It forms when a pocket of pus develops in the tissue between the tonsil and the throat wall, usually as a complication of untreated or inadequately treated tonsillitis. The pain is intense and one-sided, and it tends to escalate quickly over a day or two.

The symptom profile is distinctive. Beyond severe sore throat, patients commonly report difficulty swallowing, painful swallowing, and a characteristic “hot-potato” voice, a muffled quality that sounds like you’re trying to talk around something stuck in your mouth.¹ Trismus, where opening your mouth becomes painful or nearly impossible, occurs in about a third of peritonsillar abscess cases.² Ear pain on the same side is also common, even though the ear itself is fine; the shared nerve pathways between the throat and the ear create this referred pain.

Peritonsillar abscesses need medical treatment. In rare cases, a spontaneous rupture can lead to severe bleeding that requires emergency surgery.³ Even without that dramatic complication, the infection can spread into the deeper spaces of the neck if left untreated.

What Happens Inside the Tonsil Versus Around It

An important distinction that even many clinicians initially miss is whether the abscess sits outside the tonsil capsule (a peritonsillar abscess, or PTA) or inside the tonsil itself (an intratonsillar abscess, or ITA). The symptoms overlap heavily: sore throat is present in roughly 97% of both types. But there are clues. Intratonsillar abscesses tend to produce more fever, with about 39% of patients spiking a temperature compared to about 20% with standard peritonsillar abscesses. Meanwhile, trismus and difficulty swallowing are more pronounced with a peritonsillar abscess.² The practical difference matters because intratonsillar abscesses can be harder to diagnose on a standard exam, and the standard needle aspiration approach may not reach the pus effectively.

Tonsil Stones

Tonsil stones, or tonsilloliths, are hardened lumps of debris that form in the small pockets and folds of the tonsils. Food particles, dead cells, and bacteria get trapped in these crypts, and over time the material mineralizes into whitish, calcified nuggets. They affect the palatine tonsils almost exclusively and can show up on one side or both.⁴

Most tonsil stones are small and cause no symptoms at all. When they do cause problems, the most common complaint is bad breath, followed by a feeling of something being stuck in the throat, mild pain, or a heaviness when swallowing.⁴ The discomfort from a tonsil stone is usually more annoying than alarming. It’s a dull ache or a scratchy sensation, not the sharp, escalating pain you’d feel with an abscess. If you can see a yellowish-white lump on your tonsil surface when you look in the mirror, there’s a good chance that’s what you’re dealing with.

Small stones can sometimes be dislodged with gentle pressure from a cotton swab or even vigorous gargling with salt water. Larger or recurrent stones may need attention from a doctor. Tonsil stones also account for a fair share of one-sided tonsil swelling, which can look alarming but is virtually always benign.⁵

Glossopharyngeal Neuralgia

If your left tonsil pain comes in sudden, electric-shock-like bursts rather than a steady ache, the cause might be nerve-related. Glossopharyngeal neuralgia is a rare condition where the ninth cranial nerve fires intense pain signals that hit the base of the tongue, the tonsil, the area beneath the angle of the jaw, or the ear canal.⁶ The pain is typically one-sided and can be triggered by swallowing, talking, coughing, or even yawning.⁷

The episodes tend to be brief but excruciating. One published case described a patient with left-sided, intermittent, swallow-triggered electrical pain radiating from the ear to the throat.⁸ Some people with this condition also experience fainting or a dangerous drop in heart rate during an attack, because the glossopharyngeal nerve is closely tied to the vagus nerve, which regulates heart rhythm.

The key distinguishing feature is the quality of the pain. Infections produce a constant, throbbing soreness that worsens gradually. Glossopharyngeal neuralgia produces sharp, stabbing jolts that last seconds to minutes, then vanish completely between episodes. If that pattern sounds familiar, it’s worth bringing up with a neurologist rather than continuing to treat what you assume is a recurring infection.

Eagle Syndrome and Structural Causes

There’s a small, pointed piece of bone called the styloid process that juts downward from the base of the skull, just behind the tonsil region. Normally it’s about two to three centimeters long and doesn’t cause problems. In some people, it grows longer than three centimeters or the ligament attached to it calcifies, creating a bony projection that presses against nearby structures. This is called Eagle syndrome.⁹

The symptoms can mimic a chronic sore throat: pain in the tonsil region, difficulty swallowing, a sensation of something stuck in the throat, and referred ear pain. The discomfort may get worse when you turn your head or open your mouth wide. Eagle syndrome is diagnosed with imaging, usually a CT scan that reveals the elongated styloid process. It’s uncommon, but it’s a reasonable thing to consider if you have persistent one-sided throat pain with no sign of infection and no response to antibiotics.

Why One-Sided Tonsil Swelling Needs Attention

When one tonsil is noticeably larger than the other, people understandably worry about cancer. The reassuring reality is that most one-sided tonsil swelling traces back to common causes: a past episode of tonsillitis, a previous peritonsillar abscess, or tonsil stones.⁵ Other benign explanations include mucus retention cysts, lipomas, and polyps. Asymmetry by itself, without other symptoms, rarely turns out to be malignant.

A study looking at over 300 patients who had a tonsil removed because of unilateral enlargement found no malignancies in any of the pediatric cases. Among adults, five cases of cancer were identified, and every one of them presented with other symptoms beyond the enlarged tonsil.¹⁰ The single strongest predictor of a malignant outcome was a history of rapid unilateral tonsil enlargement, meaning the tonsil grew bigger over weeks rather than having always been slightly larger on one side.

When tonsillectomies are performed for suspicious reasons, the picture changes. In one analysis, roughly a third of cases biopsied for suspicious indications turned out to be malignant, with squamous cell carcinoma being the most common type and the vast majority linked to HPV infection.¹¹ The takeaway isn’t that one-sided tonsil pain should make you panic, but that certain red-flag symptoms alongside that pain justify a prompt visit to your doctor.

Red Flags That Warrant a Doctor Visit

For straightforward sore throats, even one-sided ones, you can usually wait a few days and see if things improve. But certain symptoms should prompt you to seek care sooner rather than later.

Difficulty breathing or swallowing saliva: If you can’t swallow your own saliva, or if you’re drooling because swallowing has become too painful, you need urgent evaluation. This can signal a peritonsillar abscess or a deep neck infection pressing on your airway.
Inability to open your mouth: Trismus, severe enough that you can barely fit a finger between your teeth, suggests the infection has moved beyond the tonsil surface into the surrounding tissues.
Muffled or changed voice: A new “hot-potato” quality to your voice, where you sound like you’re speaking around a mouthful of food, often accompanies abscess formation.
High fever and worsening pain after several days: A sore throat that initially seems to improve and then gets dramatically worse, especially with fever climbing above 101°F, may indicate an abscess developing.
Unexplained weight loss, night sweats, or blood in saliva: These are red flags for possible malignancy and call for referral to an ear, nose, and throat specialist.⁵
Persistent one-sided pain lasting more than two weeks: Especially if accompanied by ear pain on the same side, hoarseness, or a lump in the neck.
Rapid enlargement of one tonsil: A tonsil that visibly grows over a matter of weeks in an adult should be evaluated, as rapid unilateral growth was the strongest predictor of malignancy in the largest available case series.¹⁰

Deep neck infections are a particular concern because they can worsen fast. One case report described a patient with diabetes who came to the emergency department after five days of worsening jaw pain, facial swelling, trismus, and voice changes, and imaging revealed a large collection of pus in the deep neck space requiring emergency surgery.¹² That case started as dental pain, a reminder that not all throat pain originates in the throat. A bad tooth, an impacted wisdom tooth, or a jaw infection can refer pain to the tonsil area on the same side.

How Peritonsillar Abscesses Are Treated

If you do end up diagnosed with a peritonsillar abscess, the standard treatment is to drain the pus. Two main approaches are used: needle aspiration, where a needle is inserted into the abscess to draw out the fluid, and incision and drainage, where a small cut is made to let the pus out. Both are effective. Incision and drainage tends to have a higher first-attempt success rate and allows more complete drainage, while needle aspiration is less invasive and can be done with less discomfort.¹³

A Cochrane review pooling data from ten studies found a higher recurrence rate after needle aspiration compared to incision and drainage, but the authors noted the evidence quality was very low.¹⁴ In practice, many clinicians start with needle aspiration because it’s simpler and works well for most patients. One comparative study found roughly three-quarters of needle aspiration cases and about four-fifths of incision and drainage cases resolved successfully without needing a repeat procedure.¹⁵ If the first attempt doesn’t work, the doctor can escalate to a more aggressive approach.

Antibiotics are always part of the treatment plan alongside drainage. In some cases, steroids are added to reduce swelling and pain. If abscesses keep coming back, or if you’ve had several bouts of severe tonsillitis on one side, a tonsillectomy on the affected side may be recommended. One long-term review of unilateral tonsillectomies found that about two-thirds of patients experienced a dramatic improvement in symptoms, though roughly one in ten eventually developed compensatory enlargement of the remaining tonsil and needed it removed too.¹⁶

Children Versus Adults

One-sided tonsil pain in a child is far less concerning from a cancer standpoint than the same symptom in an adult. In the multi-center study of over 300 unilateral tonsil enlargement cases, none of the 90 pediatric patients had malignancy.¹⁰ Children commonly have larger, more reactive tonsils than adults, and it’s not unusual for one tonsil to look bigger than the other simply because it responded more vigorously to a recent cold. Pediatric tonsillitis also tends to recur more frequently; the tonsils are more immunologically active in childhood and catch more of what passes through the mouth.

For adults, one-sided tonsil pain that persists beyond a reasonable window for infection deserves more scrutiny. HPV-associated oropharyngeal squamous cell carcinoma has been rising in prevalence in middle-aged adults, and the tonsil is one of its most common sites. The malignancies found in the study mentioned earlier were all in adults and all had additional symptoms beyond swelling alone. This doesn’t mean every adult with a sore left tonsil needs a biopsy, but it does mean that accompanying symptoms like referred ear pain, unexplained weight loss, or a neck lump shouldn’t be dismissed.

Referred Pain From Outside the Throat

Not everything that feels like tonsil pain actually originates in the tonsil. The throat sits at a busy crossroads of nerve pathways, and pain can be referred there from several other locations. Dental infections, particularly in the lower molars or impacted wisdom teeth, can send pain straight to the tonsil area on the same side. Temporomandibular joint problems, where the jaw joint becomes inflamed or misaligned, can produce deep aching around the tonsil and ear. Even acid reflux, when stomach acid washes up high enough to reach the back of the throat, can irritate one side more than the other and create a chronic burning or raw sensation that mimics tonsillitis.

This is worth keeping in mind if you’ve been treated for a throat infection and the pain isn’t resolving. If antibiotics and time haven’t helped, the pain generator might not be where you think it is. Mentioning recent dental work, jaw clicking, or heartburn to your doctor can help steer the evaluation toward the actual source.

1
PubMed Central. Spontaneous Rupture of a Peritonsillar Abscess Mimicking Successful Incision and Drainage: A Case Report
2
PubMed Central. A hidden diagnosis in the tonsil: recognising and differentiating intratonsillar abscess
3
PubMed Central. Spontaneous Life-Threatening Hemorrhage Secondary to a Peritonsillar Abscess Requiring Intervention and Local Flap Reconstruction
4
PubMed Central. World’s Largest Tonsillolith Removal: A Case Report With Literature Review of Large Tonsil Stones on Record
5
Journal of Otolaryngology-ENT Research. Unilateral tonsillar swelling: role and urgency of tonsillectomy
6
PubMed Central. An uncommonly common: Glossopharyngeal neuralgia
7
International Journal of Medical Case Reports. Case Report: Radiofrequency Pulsed Therapy for Glossopharyngeal Neuralgia with Associated Syncope
8
PubMed Central. Concurrent Glossopharyngeal Neuralgia and Hemi-Laryngopharyngeal Spasm (HeLPS): A Case Report and a Review of the Literature
9
PubMed Central. Eagle syndrome with bilateral stylohyoid ossification: a surgical case report with anatomical correlation
10
PubMed. Unilateral tonsil enlargement in children and adults: is routine histology tonsillectomy warranted? A multi-centre series of 323 patients
11
PubMed. Incidence of Occult Malignancy Diagnosed on Histopathology in Routine Adult Tonsillectomies
12
PubMed Central. A severe deep neck odontogenic infection not prioritised by the emergency department triage system and National Early Warning Score
13
PubMed Central. Comparative Clinical Outcomes of Needle Aspiration and Incision & Drainage in Peritonsillar Abscess
14
PubMed Central. Needle aspiration versus incision and drainage for the treatment of peritonsillar abscess
15
Pakistan Journal of Medical and Health Sciences. Comparative Effectiveness of Needle Aspiration Vs Incision and Drainage in Management of Peritonsillar Abscess
16
Cambridge University Press. Unilateral tonsillectomy–indications and results