Cold sores (herpes simplex)

For a lay person:

Cold sores are small blisters, usually on or around the lips, caused by the herpes simplex virus. After the first infection the virus stays in the body and can reactivate with stress, illness, sunlight or tiredness. Outbreaks usually heal within one to two weeks but can spread to others by close contact.

For a trained medical person:

Herpes simplex virus type 1 (and sometimes type 2) establishes latency in sensory ganglia and reactivates to cause orolabial lesions; primary infection may present as gingivostomatitis. Diagnosis is clinical, with PCR of lesion swabs when uncertain. Treatment is supportive, with topical or oral antivirals started early for frequent or severe outbreaks and suppressive therapy for frequent recurrences or immunocompromised people.

In Chinese medicine:

Liu and Tseng's textbook differentiates this condition into these patterns: Wind-Heat and Damp-Toxin; Qi and Yin Deficiency. Treatment follows the pattern a patient presents with, not the Western diagnosis alone.

When to get help: See a doctor urgently for sores near the eye, a cold sore in a newborn, a weakened immune system, widespread blisters on eczema, or fever with confusion or severe headache. Avoid kissing babies while you have a cold sore.