Cold sores

• primary oral infection with the herpes simplex virus (HSV)
  • typically occurs at a young age
  • is asymptomatic
• after primary oral infection, HSV may persist in a latent state in the trigeminal ganglion
  • it may later reactivate as the more common herpes labialis, or "cold sores." (1)
• these are recurrent herpes simplex infection around the mouth.
• these lesions have a variable recurrence rate and may be associated with respiratory infections.
• their occurence may be also related to non-specific factors such as:
  • emotional stress
  • menstruation
  • sunshine
• the classical manifestation is a well-localized cluster of small vesicles along the vermilion border of the lip or adjacent skin
  • the vesicles rupture, ulcerate, and crust within 24 to 48 hours
  • they spontaneously heal over seven to 10 days

Public Health England guidance states (2):

• most resolve after 5 days without treatment
• topical antivirals applied prodromally can reduce duration by 12 to 18 hours
• if frequent, severe, and predictable triggers:
  • consider oral prophylaxis: aciclovir 400mg, twice daily, for 5 to 7 days

Reference:

• (1) Wanda C. Gonsalves .Common Oral Lesions: Part I. Superficial Mucosal Lesions. Am Fam Physician 2007;75:501-7.
• (2) Public Health England (June 2021). Managing common infections: guidance for primary care