When a person notices a “blister” in their throat, they are typically observing a lesion that falls into one of three medical categories: a vesicle, a bulla, or an ulcer. A vesicle is a small, elevated, fluid-filled sac, while a bulla is a larger version. Because the throat’s lining (mucosa) is thin and moist, these fluid-filled structures rupture easily due to friction from swallowing or speaking. The resulting open sore is called an ulcer, which appears as a painful, shallow, yellowish-white defect surrounded by a red border. Identifying the underlying cause of these lesions is crucial because management varies significantly, ranging from self-limiting viral infections to severe systemic conditions.
Viral Agents
The most frequent causes of throat lesions are viral infections, particularly those caused by the Coxsackievirus group. Two distinct conditions arise from this infection, both characterized by blister formation in the pharynx. Herpangina, caused by various serotypes, primarily targets the posterior region of the mouth and throat. This infection produces small, discrete lesions that begin as reddish spots, quickly develop into vesicles, and then break down into characteristic ulcers, typically located on the soft palate, tonsillar pillars, and uvula.
Another common Coxsackievirus manifestation is Hand, Foot, and Mouth Disease (HFMD). HFMD causes lesions in the mouth, often alongside a rash on the palms and soles. The oral lesions start as small, red spots that evolve into vesicles and then painful ulcers on the tongue, gums, and inside of the cheeks. Both Herpangina and HFMD are highly contagious and primarily affect children, though adults can also contract them during summer and fall epidemics.
Another significant viral agent is the Herpes Simplex Virus (HSV), typically Type 1, which causes primary herpetic gingivostomatitis during the first exposure. This infection produces clusters of tiny, fluid-filled blisters that can appear anywhere in the mouth or throat. These vesicles quickly rupture to form painful ulcers, often accompanied by fever, body aches, and swollen lymph nodes. While subsequent HSV outbreaks usually present as cold sores on the lips, the initial infection can be severe and widespread across the oral and pharyngeal mucosa.
Non-Infectious Damage
Blister-like lesions in the throat can also result from direct physical, thermal, or chemical damage rather than an infection. Thermal injury, such as a burn from swallowing excessively hot food or liquids, can immediately cause the superficial layer of the mucosa to separate. This separation results in a bulla or a large, raw erosion that mimics a blister. These traumatic lesions are painful and may take several days to heal.
Mechanical trauma can also initiate the formation of a localized ulcer or erosion in the pharynx. Aggressive coughing or retching can cause minor tears in the throat lining. Similarly, medical procedures like intubation during surgery can lead to localized injury and subsequent ulceration on the vocal cords or the back of the throat. Constant friction or localized pressure from these factors prevents normal healing, leading to a persistent sore spot.
Chemical irritation is another non-infectious cause, most commonly seen with severe or chronic acid reflux, known as Gastroesophageal Reflux Disease (GERD) or Laryngopharyngeal Reflux (LPR). The backflow of harsh stomach acid and digestive enzymes repeatedly erodes the delicate lining of the esophagus and pharynx. This chemical burn causes inflammation and shallow erosions that can resemble open sores or ruptured blisters, leading to a sore throat and difficulty swallowing.
Autoimmune and Inflammatory Conditions
A distinct set of causes involves systemic autoimmune or inflammatory responses where the body mistakenly attacks its own mucosal tissues. Pemphigus Vulgaris is a rare autoimmune disease where antibodies target proteins that hold cells together, causing them to detach. This leads to the formation of thin-walled, fragile bullae on the mucous membranes, including the throat. These blisters rupture almost immediately, leaving behind chronic, painful erosions that are often the first sign of the disease.
Stevens-Johnson Syndrome (SJS) and its more extensive form, Toxic Epidermal Necrolysis (TEN), are severe inflammatory reactions often triggered by certain medications. These conditions cause the mucous membranes of the mouth, throat, eyes, and genitals to blister and slough off. The rapid development of extensive mucosal blistering leads to widespread ulceration, which can make swallowing and breathing difficult.
Less severe, but often confused with true blisters, are recurrent aphthous ulcers, commonly known as canker sores. These are inflammatory lesions linked to immune system irregularities, stress, or nutritional deficiencies, not caused by a virus or trauma. Unlike viral vesicles, aphthous ulcers in the throat appear as isolated, round or oval sores with a gray base and a distinct red halo, without a clear fluid-filled stage.
Diagnosis and Management
When a patient presents with lesions in the throat, a healthcare provider begins the diagnostic process with a visual inspection and detailed patient history. The location, size, and number of the lesions are crucial clues; for example, lesions clustered on the posterior pharynx suggest Herpangina, while widespread blistering points toward a systemic cause. Patient history focuses on recent exposures, medication use, and the presence of other symptoms like fever, skin rashes, or difficulty eating.
If an infectious cause is suspected, diagnostic tools may include a throat swab to culture for bacteria or a Polymerase Chain Reaction (PCR) test to detect viral DNA (e.g., HSV or Coxsackievirus). Management is centered on symptomatic relief and preventing complications while the underlying condition resolves. For most viral causes, treatment is supportive, focusing on controlling pain and fever with medications like acetaminophen or ibuprofen.
Hydration is a primary concern, as the pain from the sores often prevents adequate fluid intake, especially in children. Patients are encouraged to use topical anesthetic mouth rinses to temporarily numb the area before eating or drinking. Immediate medical attention is necessary if a person experiences signs of severe systemic illness, such as a high, persistent fever, inability to swallow fluids, or difficulty breathing due to throat swelling.