What Causes Cold Sores at the Corners of the Mouth?

Common triggers for cold sores (herpes labialis) at the corners of the mouth include infection with the herpes simplex virus (HSV), decreased immunity, local skin damage, unhealthy lifestyle habits, and contact transmission. The virus remains latent within the body and becomes reactivated upon exposure to various triggers, leading to the formation of painful, fluid-filled blisters at the oral commissures. If the lesions spread extensively or are accompanied by persistent fever, prompt medical evaluation and treatment are recommended.

1. Herpes Simplex Virus Infection:

After entering the body, the virus establishes latency within sensory nerve ganglia. When systemic conditions change—such as during stress or illness—the virus reactivates, travels along nerve pathways to the skin at the corner of the mouth, replicates within epidermal cells, and triggers localized inflammation. This results in clusters of small, painful vesicles accompanied by a burning or stinging sensation.

2. Decreased Immunity:

Staying up late, excessive physical or mental fatigue, or recovering from a serious illness can all impair immune function, reducing the body’s ability to suppress latent HSV. Lowered immunity increases susceptibility to outbreaks, raises the risk of recurrence, and slows healing.

3. Local Skin Damage:

Dryness, cracking, or minor abrasions at the corners of the mouth compromise the skin’s protective barrier, facilitating viral entry into the tissue and increasing the likelihood of reactivation of latent virus. Frequent lip-licking exacerbates dryness and cracking, thereby raising the risk of outbreak.

4. Unhealthy Lifestyle Habits:

Long-term consumption of spicy or irritating foods and chronic psychological stress disrupt internal homeostasis. Altered blood circulation around the mouth reduces local skin resistance, promoting viral reactivation and recurrent cold sores.

5. Contact Transmission:

Sharing utensils or towels contaminated with HSV—or close contact with an individual actively shedding the virus—can lead to transmission. The virus may persist on surfaces; touching such objects and then touching the mouth may result in primary infection and subsequent lesion development.

Avoid puncturing or scratching the blisters, as this may cause viral spread and new lesions. Keep the perioral area clean and dry, follow a bland diet, maintain regular sleep patterns, and adopt healthy habits to shorten the duration of cold sore recovery.