Is cold sores serious?
Last updated September 6, 2026.
Usually not: most cold sores heal on their own within one to two weeks, though a few situations do need prompt medical care. Cold sores come from herpes simplex virus, most often type 1, which stays in the body and can reactivate after illness, stress, sun exposure, or hormonal changes. The answer changes when the virus reaches places it should not go, such as the eye, broken eczema skin, or a newborn, and when your immune system is suppressed by medication or illness. Prescription antiviral pills like acyclovir or valacyclovir shorten an outbreak most when you start them at the first tingle, before blisters form. Keeping the area clean, using lip balm with sunscreen, and not touching or picking the sore lowers the chance of spreading it to others or to your own eyes. Cold sores are contagious through kissing, shared drinks, utensils, towels, and oral sex, including in the days before a blister appears.
What to do
- Treat at the first tingle: Antiviral pills and creams shorten an outbreak most when you start within the first day of symptoms.
- Protect your eyes: Wash your hands after touching a sore and call a clinician the same day if you get eye pain, redness, or blurred vision.
- Avoid contact with newborns: Do not kiss a baby under 3 months while you have a cold sore, since infection at that age can be severe.
- Tell your clinician about eczema: A cold sore that spreads across eczema skin needs urgent treatment rather than home care.
- Track your triggers: Note whether sun, illness, stress, or your cycle sets off outbreaks, and use SPF lip balm if sunlight is one.
- Ask about suppressive therapy: If you get frequent outbreaks, daily antiviral medication is a reasonable option to discuss with a clinician.
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