An ulcer on the tonsil is a break in the protective mucosal lining of the tonsil or the surrounding throat tissue. When this resilient layer is compromised, it exposes underlying tissue and can cause significant pain, especially during swallowing. The tonsils are lymphatic tissue that acts as a first line of immune defense, constantly exposed to foreign invaders and irritants. Although an ulcer can be concerning, most causes are common, temporary, and treatable.
Infectious Causes of Tonsil Ulcers
The most frequent cause of tonsil ulceration involves viral agents that specifically target the mouth and throat tissue. These infections often present with systemic symptoms, indicating a generalized illness rather than a localized injury.
Mononucleosis, caused by the Epstein-Barr Virus (EBV), commonly leads to a severe sore throat and swollen tonsils that can develop ulcerations. These lesions are accompanied by fatigue, fever, and swollen lymph nodes, particularly in the neck. The tonsils may also display a whitish-yellow coating or exudate, sometimes making it difficult to distinguish from a bacterial infection.
The Herpes Simplex Virus (HSV) typically causes cold sores but can also manifest as ulcers on the tonsils and throat, especially during a primary infection. These painful lesions start as small, fluid-filled blisters that quickly rupture to form ulcers, frequently appearing in clusters. Coxsackievirus, the agent behind Hand, Foot, and Mouth Disease, causes a specific throat infection called Herpangina, resulting in small, blister-like ulcers located predominantly on the soft palate and tonsils.
Bacterial infections, such as Group A Streptococcus (strep throat), typically cause severe inflammation and exudate rather than true ulcers. However, an uncontrolled bacterial infection can spread to adjacent tissue, forming a deep pocket of pus known as a peritonsillar abscess. This complication presents with severe, usually unilateral, throat pain, a muffled voice, and difficulty opening the mouth, requiring immediate medical attention.
Physical Trauma and Common Non-Infectious Irritations
Ulcers can also result from a direct physical breach of the mucosal surface without any infectious agent. This mechanical injury is a common cause, often occurring from everyday activities.
Consuming hard or sharp foods, such as chips, crusty bread, or small bones, can scratch the delicate tissue of the tonsillar pillars or the tonsil, creating an ulceration. Aggressive dental procedures, intubation during surgery, or vigorous coughing can also cause enough friction or trauma to initiate a localized break in the lining. Traumatic ulcers typically have an irregular shape and begin healing rapidly once the source of irritation is removed.
Aphthous ulcers, commonly known as canker sores, are a frequent non-infectious cause that can appear on the tonsil or surrounding soft tissue. These distinct lesions present as a small, round or oval sore with a white or yellowish center and a red, inflamed border. They are often triggered by emotional stress, nutritional deficiencies (like low B12 or folate), or minor trauma, and they are not contagious.
The tonsil area is sensitive to chemical and thermal irritants. Acidic foods (like tomatoes or citrus fruits), hot beverages, and harsh ingredients in mouthwashes can irritate the mucosal lining, predisposing it to ulceration. This irritation is often exacerbated by chronic acid reflux (GERD), where stomach acid repeatedly contacts the back of the throat, leading to persistent inflammation and potential ulcer formation.
Ulcers Related to Systemic Inflammation
In rarer instances, a tonsil ulcer may be an external symptom of a systemic disease affecting the entire body. These conditions cause inflammation that leads to ulcer formation in multiple mucosal linings.
Certain autoimmune disorders, like Behçet’s disease, are characterized by recurrent, painful oral ulcers that can involve the tonsils, often accompanied by genital ulcers and eye inflammation. Their frequent recurrence and association with other symptoms suggest an underlying systemic condition. Inflammatory Bowel Diseases (IBD) such as Crohn’s disease can also manifest with oral ulcers, sometimes years before the onset of intestinal symptoms.
Individuals with compromised immune systems, such as those undergoing chemotherapy or with chronic illnesses, may develop persistent ulcers due to opportunistic infections or impaired healing. In these cases, the body’s normal defensive mechanisms are insufficient to clear minor tissue breaches. These systemic causes are less common but indicate that the tonsil ulcer is a sign of a broader issue.
Red Flags and When to Seek Medical Care
Most tonsil ulcers resulting from common viral infections or minor trauma are self-limiting, healing on their own within one to two weeks. Comfort measures during this period include over-the-counter pain relievers, maintaining hydration, and gargling with warm saltwater. A soft, non-acidic diet can also prevent further irritation.
However, certain signs should prompt a medical evaluation to rule out a more serious diagnosis. The most important red flag is an ulcer that persists without improvement for more than two to three weeks. A non-healing, solitary ulcer, especially if it feels firm, rapidly enlarges, or is painless, must be investigated immediately, as it can rarely be a sign of oropharyngeal cancer.
Other warning signs requiring urgent medical attention include difficulty breathing, severe pain that prevents swallowing liquids, drooling, or a muffled “hot potato” voice. This combination of symptoms can indicate a peritonsillar abscess, which is a medical emergency due to the risk of airway obstruction. Unexplained weight loss, persistent high fever, or a swollen lymph node in the neck that does not resolve should also be evaluated promptly.