What Causes Small Blisters at the Corners of the Mouth?

The symptom of skin blisters is relatively conspicuous and may cause pain and itching at the blistered sites. In some individuals, small blisters around the mouth may arise from highly complex etiological factors. So, what causes small blisters at the corners of the mouth? Below, we provide an explanation.

Causes of Small Blisters at the Corners of the Mouth

1. Excess Internal Heat (“Shanghuo”)

Blisters around the mouth may result from improper diet. Patients who chronically neglect hydration or frequently consume spicy, irritating foods are prone to developing “excess internal heat,” which can manifest as blisters around the mouth.

2. Herpes

Small blisters at the corners of the mouth are not solely attributable to excess internal heat but may also be caused by herpes infection. Oral herpes commonly occurs during periods of lowered immunity—such as during colds, fevers, or menstruation—and presents as small blisters around the lips. It is highly contagious.

3. Aphthous Ulcers (Canker Sores)

Blisters at the corners of the mouth may also stem from aphthous ulcers. These ulcers are often triggered by allergic reactions, infections, fatigue, or vitamin deficiencies. Such blisters typically resolve spontaneously within one to two weeks.

4. Oral Leukoplakia

Oral leukoplakia represents a direct mucosal response to external irritants—for example, ill-fitting dentures, chronic smoking, or prolonged exposure to wind and sun. It most commonly affects the lips, tongue, gingiva, and floor of the mouth. Early-stage lesions are usually asymptomatic; however, if erosion or ulceration develops, severe pain may ensue. Should the plaques suddenly enlarge or thicken rapidly, this warrants special attention, as it may signal a precancerous lesion.

5. Oral Thrush (Candidiasis)

Oral thrush is a fungal infection characterized by white, snowflake-like patches, predominantly affecting the buccal mucosa, tongue, soft palate, and inner lips. Infants and young children are especially susceptible. Common sources of infection include inadequate sterilization of bottles and nipples, habitual finger-sucking, or poor hygiene of the mother’s nipples during breastfeeding. Additionally, elderly individuals undergoing long-term antibiotic therapy are also at increased risk. A comprehensive oral examination at a hospital is strongly recommended.

The above outlines the potential causes of small blisters at the corners of the mouth. We hope this information proves helpful.