Cold sores result primarily from HSV-1 and recur because the virus stays latent in nerve cells. Over-the-counter docosanol (Abreva) and prescription antivirals (acyclovir, valacyclovir, famciclovir, penciclovir) shorten and ease outbreaks when started early. Supplements and many branded topicals have limited or mixed evidence. Prevent spread by avoiding contact during active sores and by managing triggers. See a clinician for frequent, severe, or complicated cases. No approved HSV-1 vaccine or cure exists as of this update.
What causes fever blisters
Fever blisters, commonly called cold sores, are almost always caused by herpes simplex virus type 1 (HSV-1). HSV-2 can also cause oral sores but is more often associated with genital infection. The virus remains in nerve cells and can reactivate, causing recurrent sores. While you cannot cure HSV, you can treat and shorten outbreaks.
Over-the-counter and prescription options
Topical docosanol (brand name Abreva) is an over-the-counter option that can modestly shorten healing time if you apply it at the first tingle or prodrome. Prescription oral antivirals - acyclovir, valacyclovir (Valtrex), and famciclovir (Famvir) - reduce pain, speed healing, and lower contagiousness when started early.
Topical prescription creams such as penciclovir (Denavir) can also reduce duration if begun at the first sign of a sore. For frequent or severe outbreaks a clinician may recommend suppressive daily oral antiviral therapy to reduce recurrence and transmission.
Some nutritional supplements (most commonly L-lysine) and a variety of branded topical products (for example, ViraDerm or Viroxyn) are marketed for cold sores. Evidence for supplements and many commercial topical products is mixed or limited; they are not a substitute for proven antiviral medications.
Practical self-care and trigger management
Start treatment at the first warning sign (tingling, itching). Keep the area clean and avoid picking at blisters. Over-the-counter pain relievers or topical analgesics can reduce discomfort. Lip sunscreen and avoiding known triggers (sun exposure, extreme cold, stress) help reduce recurrences.
HSV spreads through close contact, saliva, or sharing items like utensils and lip products. Avoid kissing and oral contact with others while sores are active.
When to see a doctor
Seek medical care if you have very frequent outbreaks, unusually large or painful sores, signs of bacterial infection, a compromised immune system, or if an infant or immunocompromised person is exposed. A clinician can prescribe oral antivirals and advise on suppressive therapy if needed.
What about vaccines and a cure?
As of this update there is no widely available, approved vaccine that prevents HSV-1 infection and no cure that eradicates latent virus. Research continues, but prevention relies on behavioral measures and antiviral medications.
Bottom line
Cold sores are common, recurrent, and contagious. Early treatment with topical or oral antivirals shortens outbreaks and reduces symptoms. Discuss frequent or severe outbreaks with a healthcare provider to consider suppressive therapy or other options.
- Confirm regulatory status and published clinical evidence for branded products ViraDerm and Viroxyn.
- Confirm current prescription/OTC status of penciclovir (Denavir) in the U.S. market.
- Confirm there is no approved HSV-1 vaccine as of this date (2025-08-21).