What is the treatment for fever blisters?

Treatment for Fever Blisters (Herpes Labialis/Cold Sores)

Initiate oral antiviral therapy at the earliest sign of prodromal symptoms (tingling, itching, burning) with either famciclovir 1500 mg as a single dose, valacyclovir 2000 mg twice daily for one day, or acyclovir 400 mg five times daily for 5 days. 1, 2, 1

First-Line Antiviral Treatment

The FDA-approved oral antiviral agents for herpes labialis are highly effective when started early:

• Famciclovir 1500 mg as a single dose is the most convenient option and should not exceed one dose for cold sore treatment 1
• Valacyclovir 2000 mg twice daily for one day (two doses 12 hours apart) provides comparable efficacy with better bioavailability than acyclovir 2, 3
• Acyclovir 200-400 mg five times daily for 5 days is effective but requires more frequent dosing 4, 3

Timing is critical: treatment must begin at the first sign of prodromal symptoms (tingling, itching, burning, pain) or when the lesion first appears to maximize effectiveness. 1

Local Wound Care

While antivirals address the viral infection, proper blister management reduces complications:

• Leave intact blisters completely alone whenever possible, as the blister roof serves as a natural biological dressing 5, 6
• Gently cleanse with antimicrobial solution (dilute chlorhexidine or saline) without rupturing the blister 7, 5, 6
• If drainage is necessary, pierce at the base with a sterile needle (bevel up), apply gentle pressure with sterile gauze, but do not remove the blister roof 7, 5
• Apply bland emollient (50% white soft paraffin with 50% liquid paraffin or plain petroleum jelly) to support barrier function and reduce water loss 7, 5, 6

Infection Prevention

• Apply topical antimicrobials only to areas with clinical signs of secondary bacterial infection (increased erythema, purulent drainage, warmth), not prophylactically 5, 6
• Change dressings using aseptic technique if covering is needed 5, 6
• Obtain bacterial cultures before starting antibiotics if secondary infection is suspected 5

Key Patient Counseling Points

• Antivirals are not a cure for herpes labialis; they reduce symptom duration and severity 1
• Avoid contact with lesions and refrain from kissing or sharing utensils/towels to prevent transmission to others 1
• Viral shedding can occur without visible lesions, so transmission is possible even when asymptomatic 1
• Famciclovir may be taken with or without food, though taking with food can reduce stomach upset 1
• Valacyclovir passes into breast milk as acyclovir; discuss risks/benefits if breastfeeding 2

Common Pitfalls to Avoid

• Do not deroof blisters, as this increases infection risk and delays healing 7, 5, 6
• Do not apply topical antimicrobials prophylactically to uninfected lesions 5, 6
• Do not delay treatment; efficacy decreases significantly if antivirals are started more than 24-48 hours after symptom onset 1
• Do not use acyclovir-resistant protocols (foscarnet, cidofovir) in immunocompetent patients without documented resistance 4

Special Populations

• Pediatric patients ≥12 years: Use the same adult dosing regimens for cold sores 2
• Pregnant women: Valacyclovir and acyclovir have been used during pregnancy with no consistent evidence of harm, though data are limited 2
• Immunocompromised patients: May require longer treatment courses (7-10 days) and higher doses; consider acyclovir resistance if lesions fail to respond after 5-7 days of standard therapy 4