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Herpes Labialis (Cold Sores)

R. Vender MD FRCPC1 and B. Kuehl PhD2
1 Dermatrials Research, Hamilton, Ontario, Canada
2 Scientific Insights Consulting Group, Mississauga, Ontario, Canada


While cold sores may be considered mild and inconsequential compared with many other viral infections, they can be extremely uncomfortable physically, making it painful to eat and talk.
Cold sores also cause a huge emotional impact as sufferers change their routines to avoid being seen with an unsightly sore and to prevent spreading the virus to their family and close acquaintances.

Treatment options are available to reduce the discomfort associated with cold sores and to lessen the duration of the outbreak. The newest and most promising clinically demonstrated treatments available are docosanol, a nonprescription viral entry blocking agent, valacyclovir, an antiviral prescription agent, and, soon to be approved antiviral agent, famciclovir.
More detailed information on these new treatments can be found in the Continuing Education session Recurrent Herpes Labialis: Assessment and Treatment (at


Cold sores are most often caused by herpes simplex virus type-1 (HSV-1). Primary infections are usually acquired in early childhood, often from parents or siblings, and more than 70% of children are infected by the age of 14. Once the patient is infected with HSV-1, the virus lies dormant in nerve cells. Reactivation is unpredictable with variable onset and recurrence although it can occur particularly during times of stress or trauma.
This recurrent infection can manifest itself as classical cold sores and frequently results in asymptomatic shedding of virus particles. Recurrent HSV-1 lesions occur in approximately 20%-40% of infected individuals.


Diagnostic Features of Cold Sores

Herpes labialis is an infection caused by the herpes simplex virus, characterized by an eruption of small and usually painful blisters on the skin of the lips, mouth, or the skin around the mouth. These blisters are commonly called cold sores or fever blisters.

Cold sores proceed through seven distinct stages from the prodromal stage (pain, burning, itching, or tingling at the site where the blisters will form) that precedes the blisters to the highly infectious blister to the hard scab. It is important to understand the stages and visual appearance of a cold sore, as treatment is most effective when started at the early stages.

A chart fully describing the stages of a cold sore with images can be found at Patients also often confuse cold sores with canker sores as they share certain physical characteristics. Distinguishing cold sores from canker sores is important because the two conditions have distinct etiologies, presentations, and outcomes. Cold sores are usually on the outside of the lip or on the skin around the mouth. Canker sores are usually on the inside of the lip or mouth on the mucous membranes or buccal mucosa.



Prevention of a future outbreak is important to infected individuals. Patients should be counselled to:
  • limit sun exposure and apply sun block frequently to the lips and surrounding skin before going out.
  • avoid triggers that can reactivate the virus such as windburn, UV light (sun and tanning booths), dry lips, emotional stress, and fatigue.
  • be aware of unpreventable triggers such as
  • menstruation, fever, illness, allergic reactions, physical injury, dental injury, and facial trauma.
  • exercise caution to avoid transmitting the disease to other body parts or to other individuals.


Self-Help for Prevention

  • Use skin protectants, such as moisturizers with a sun protection factor (SPF) of 30 or more, frequently on the lips and surrounding skin especially before sun or wind exposure.
  • Avoid triggering situations.
  • Get plenty of rest.
  • Learn techniques to deal with stress.
  • Do not share cutlery, cups, glasses, water bottles, towels, or razors.
  • Use proper hygiene, wash hands carefully and frequently.


Medical Treatment

Most cold sores will clear up on their own after 7-10 days. Most treatment options are focused on reducing the discomfort associated with cold sores and lessening the duration of the outbreak. There are some newer options available to prevent the outbreak from progressing beyond the prodromal stage. Things that need to be considered include initiation, duration, magnitude and frequency of the cold sore, as well as accessibility, convenience of treatment to the patient, and cost.


Non-Prescription Treatments

Symptom Support Treatments

  • Skin protectants (such as Labello® or Orabase®) provide moisturization as well as a mechanical barrier to guard the skin and lips from irritants.
  • Topical analgesics/anesthetics suppress the sensory receptors, preventing the transmission of pain sensation to the brain. They can provide temporary relief of pain and itching. Sensitization and irritation can occur from these products.
  • Oral analgesics provide temporary relief from the pain.

Viral Entry Blocking Agent Docosanol (Abreva® Cream)

  • Blocks the virus from entering cells and subsequent viral replication.
  • Has been clinically proven to reduce both the symptoms (including pain and itching) and the legth of the cold sore outbreak.
  • Most effective if it is used at the first sign or symptom of a cold sore (prodromal stage).
  • Apply 5 times per day from the time of the initial symptoms for up to 10 days.

Possible Anti-viral Activity, Zinc and Heparin (Lipactin® Gel)

  • May disrupt viral entry.
  • May help shorten the duration of the cold sore if used early during the outbreak.
  • Apply 3-6 times daily for up to 14 days.


Prescription Treatments

Anti-virals/nucleoside analogues reduce the number of infectious virions and slow infection between cells.


Acyclovir Cream/Ointment (Zovirax®)
  • Shown to help reduce the severity of cold sores in the immunocompromised.
  • Most effective if used at the first sign or symptom of a cold sore (prodromal stage).
  • Apply 4-6 times a day for 10 days.


Acyclovir (Zovirax®)
  • Reduces pain and healing time to crust formation, does not appear to affect progression, size or overall healing time.
  • Most effective if used at the first sign or symptom of a cold sore (prodromal stage).
  • Dosing: 200mg 5 times a day for 5 days.
Famciclovir (Famvir®)
  • Reduces duration, healing time, and pain.
  • Currently this drug is indicated only for treatment of recurrent episodes of HSV infections in HIV-infected patients (expanded indications are currently being explored).
  • Most effective if used at the first sign or symptom of a cold sore (prodromal stage).
  • Dosing: 500mg twice daily for 7 days.
Valacyclovir (Valtrex®)
  • Reduces duration, healing time, and pain.
  • May help suppress cold sore outbreak if taken during prodromal stage.
  • Most effective if used at the first sign or symptom of a cold sore (prodromal stage).
  • Indicated for suppression of recurrent episodes of Herpes Simplex Labialis.
  • Dosing: 2g every 12 hours for two doses.


Counseling Tips

  • Review the self-help tips with patients to help reduce their number of cold sore outbreaks and to limit transmission of the virus.
  • Counsel patients on the importance of starting treatment at the first sign or symptom of a cold sore.
  • Remind patients to wash their hands before and after applying any topical treatment to their cold sore or touching their lips.
  • Inform patients that topical treatments may be best applied with a cotton swab or a gloved finger.


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