What is the typical duration of a fever blister (cold sore)?

Duration and Management of Fever Blisters (Cold Sores)

Fever blisters (cold sores) typically last 7-10 days without treatment, but can be shortened to 5-7 days with appropriate antiviral therapy. 1, 2

Natural Course of Fever Blisters

• Fever blisters are caused by herpes simplex virus and follow a predictable pattern of development and healing 1, 3
• Without treatment, the complete episode typically lasts 7-14 days from first symptoms to complete healing 1, 4
• The progression follows distinct stages:
  • Initial symptoms (tingling, itching, burning) for 1-2 days 4, 5
  • Formation of vesicles (fluid-filled blisters) 4, 3
  • Ulceration and crusting, which is the most painful stage 4, 5
  • Healing with gradual resolution of the crust 1, 3

Treatment Options and Their Impact on Duration

Oral Antiviral Medications

• High-dose, short-duration valacyclovir (2g twice daily for 1 day) can reduce the duration of a cold sore episode by approximately 1 day compared to no treatment 1
• Starting treatment at the earliest symptoms (prodromal phase) provides the greatest benefit 1, 4
• Common oral antivirals used for cold sores include:
  • Valacyclovir - increasingly preferred due to better bioavailability 1, 2
  • Acyclovir - traditional treatment but requires more frequent dosing 2, 3

Topical Treatments

• Topical combination therapy with 5% acyclovir and 1% hydrocortisone (ME-609/Xerese) can prevent progression to ulcerative lesions in about 42% of cases when started early 4, 5
• Topical treatments alone are less effective than oral medications in reducing healing time 3, 5
• Topical antivirals should be applied 5 times daily for optimal effect 4

Factors Affecting Duration

• Early treatment initiation is the most important factor in reducing duration - treatment should begin at the first sign of symptoms 1, 4
• The stage at which treatment begins significantly impacts effectiveness 4, 5
• Individual immune status affects healing time (immunocompromised patients may experience longer duration) 3, 5
• Previous history of cold sores may influence the severity and duration of recurrences 3

Prevention Strategies

• Long-term suppressive therapy with oral antivirals can reduce the frequency of recurrences in patients with frequent outbreaks 3
• Sunscreen application can help prevent UV-induced recurrences 3
• Avoiding triggers (stress, sunlight exposure, illness) may help prevent outbreaks 5

When to Seek Medical Attention

• Fever blisters lasting more than 2 weeks 3
• Extremely painful lesions or those spreading to eyes 3, 5
• Frequent recurrences (more than 6 episodes per year) may warrant suppressive therapy 3
• Immunocompromised patients should seek medical attention for any cold sore outbreak 3, 5