Cold Sore Treatment

Cold sores are caused by herpes simplex virus type 1 (HSV-1) — and occasionally HSV-2 — which lies dormant in nerve tissue after the initial infection and reactivates periodically. Common triggers include stress, illness, fever, sun exposure, lip injury, fatigue, and hormonal changes. By adulthood, roughly half of U.S. adults carry HSV-1, though not everyone develops visible outbreaks.

Yes — cold sores are highly contagious, especially from the tingle stage through the time blisters crust over. The virus spreads through kissing, shared utensils, lip balm, towels, and any close contact with the affected area. People can also shed virus without visible lesions (asymptomatic shedding), so transmission is possible even between outbreaks.

A cold sore usually moves through five stages over 7–10 days: tingling/itching (day 1), blister formation (day 2–3), ulcer/weeping stage (day 4), crusting (day 5–8), and healing (day 8–10). Starting an oral antiviral within the first 24–48 hours — ideally at the tingle stage — can shorten the outbreak and reduce severity.

Yes. Daily SPF lip balm reduces UV-triggered outbreaks, and managing sleep, stress, and illness lowers reactivation risk. For frequent or severe recurrences (six or more per year), daily suppressive antiviral therapy with valacyclovir or acyclovir significantly reduces outbreak frequency and viral shedding.

OTC topical treatments (docosanol, acyclovir cream) may cause mild local irritation but are generally very well tolerated. Oral antivirals (valacyclovir, acyclovir, famciclovir) are well tolerated for both short-course and daily suppressive use — occasional nausea or headache is the most common effect. Renal function monitoring is recommended for prolonged daily therapy.