ConditionSkin, hair & nails
Cold Sores
Cold sores are small, painful blisters on or around the lips caused by the herpes simplex virus, usually type 1 (HSV-1). After the first infection, the virus stays dormant in nerve cells and can reactivate with triggers such as sun, stress, illness or menstruation. An outbreak starts with tingling, then blisters that burst and crust, healing in 7 to 10 days. Antiviral creams or tablets work best when started at the first tingle, and the sores are contagious until fully healed.
Also called: Fever blisters, oral herpes, herpes labialis, HSV-1 infection
At a glance
- Cause
- Herpes simplex virus, mostly HSV-1, sometimes HSV-2.
- How common
- Most adults worldwide carry HSV-1; many never have symptoms.
- Stages
- Tingling, blisters, weeping, crusting, healing over 7 to 10 days.
- Triggers
- Sun, cold wind, stress, fever or colds, periods, tiredness, dental work.
- Contagious
- Yes, from the first tingle until the skin has fully healed.
- Treatment
- Antiviral cream or tablets started early, pain relief, sun protection for prevention.
When to get help
Call 911 or go to the ER
- A cold sore with a painful red eye, sensitivity to light or blurred vision (possible herpes eye infection)
- A baby under 4 weeks old who has been near someone with a cold sore and develops fever, poor feeding, lethargy or a rash
- Widespread, rapidly spreading blisters on eczema-affected skin with fever and feeling unwell (eczema herpeticum)
See a doctor within a day or two
- A first outbreak in a child with many mouth sores, fever and refusal to drink
- Cold sores in someone with a weak immune system, such as during chemotherapy or with HIV
- A cold sore that is spreading, getting worse after 7 days, or has yellow crust and pus (possible bacterial infection)
Book a routine appointment
- Cold sores that do not heal within 2 weeks
- More than 5 or 6 outbreaks a year
- Sores that are unusually large or in unusual places
Usually safe to manage at home
- A typical cold sore on the lip that you recognize from before, in an otherwise healthy person
What causes cold sores
Cold sores are caused by the herpes simplex virus (HSV). Most are HSV-1, though HSV-2, which more often causes genital herpes, can also affect the mouth through oral sex.
The first infection usually happens in childhood through contact with saliva, for example a kiss from someone with the virus. The first episode may cause no symptoms, or a more severe illness called gingivostomatitis with many mouth ulcers, swollen gums, fever and swollen neck glands.
After that, the virus travels up the nerves and lies dormant in a nerve cluster near the ear (the trigeminal ganglion). It reactivates from time to time, travels back down the nerve and causes a cold sore, usually in the same spot.
Common triggers
- sunlight and UV exposure, including skiing
- cold, windy weather
- colds, flu and other infections with fever (hence "fever blisters")
- emotional stress and tiredness
- menstruation and hormonal changes
- injury to the lips, dental work or cosmetic procedures
- a weakened immune system
Cold sore stages
| Stage | Timing | What happens |
|---|---|---|
| 1. Tingling (prodrome) | Day 1 | Tingling, itching, burning or tightness before anything is visible |
| 2. Blisters | Days 2 to 3 | Small fluid-filled blisters appear, often in a cluster |
| 3. Weeping (ulcer) | Day 4 | Blisters burst and leave a shallow, painful, oozing sore. Most contagious stage |
| 4. Crusting | Days 5 to 8 | A yellow-brown scab forms; it may crack and bleed |
| 5. Healing | Days 8 to 10 | Scab falls off, leaving pink skin that heals without a scar |
Cold sores vs other mouth and lip sores
| Condition | Location | Features |
|---|---|---|
| Cold sore | Outside the lips, lip border | Tingling first, clustered blisters, crusting |
| Canker sore (aphthous ulcer) | Inside the mouth on soft tissue | Round white or yellow ulcer with red rim, no blisters, not contagious |
| Impetigo | Around nose and mouth | Honey-colored crusts, spreads quickly, bacterial |
| Angular cheilitis | Corners of the mouth | Cracking and redness, no blisters |
How cold sores spread
Cold sores spread by direct contact with the sore or with saliva: kissing, sharing cups, utensils, lip balm, razors or towels, and oral sex. The virus can also be shed occasionally when no sore is visible, which is how many people catch it.
You can spread it to other parts of your own body by touching the sore, especially to:
- the eyes, causing herpes keratitis, which can damage vision
- fingers, causing herpetic whitlow
- the genitals
Treatment: how to heal a cold sore faster
Cold sores clear on their own, but treatment can shorten them by a day or two and ease pain, especially if started at the tingling stage.
Over-the-counter options
- Docosanol 10% cream: apply 5 times a day, starting at the first tingle
- Pain relief: acetaminophen (paracetamol) or ibuprofen at the label dose, and numbing gels with benzocaine or lidocaine
- Petroleum jelly to stop crusts cracking
- Cold sore patches that cover the sore and reduce spread
Prescription antivirals
- Antiviral tablets such as valacyclovir, acyclovir or famciclovir. A single-day course of high-dose valacyclovir or famciclovir started at the first symptoms can shorten an outbreak
- Antiviral creams such as acyclovir or penciclovir
- Daily suppressive tablets for people with frequent or severe outbreaks, or before known triggers such as dental work or a ski trip
Self-care
- avoid touching the sore, and wash hands after applying cream
- do not pick or squeeze blisters or scabs
- use a separate towel, and avoid sharing cups or lip products
- avoid kissing, especially babies, and oral sex until fully healed
- eat soft, cool foods and avoid acidic or salty foods while sore
Prevention
- use a lip balm with SPF 30 or higher outdoors, all year
- manage stress and sleep
- take antiviral tablets before known triggers if you have frequent outbreaks
- replace your toothbrush after an outbreak
Who is at risk of complications
- Newborns: neonatal herpes is rare but can be life-threatening. People with a cold sore should not kiss newborns and should wash hands before handling them
- People with eczema: risk of eczema herpeticum, a widespread infection needing urgent treatment
- People with weakened immunity: larger, longer-lasting sores that need antiviral treatment
Frequently asked questions
How do you get rid of a cold sore fast?
Start treatment at the first tingle. Antiviral tablets such as valacyclovir or famciclovir, often as a one-day course, work best. Over-the-counter docosanol cream can also shorten healing slightly. Keep the area moist, avoid touching it and use pain relief as needed.
Are cold sores contagious?
Yes. They are contagious from the first tingling until the scab has fallen off and the skin has healed. The virus spreads through kissing, sharing cups, utensils, towels or lip products, and oral sex. It can occasionally spread when no sore is visible.
What causes cold sores to come out?
Common triggers include sun exposure, cold wind, colds and fevers, stress, tiredness, menstruation and lip injury or dental work. The virus reactivates from nerve cells where it has been dormant since the first infection.
How long does a cold sore last?
Most cold sores heal within 7 to 10 days without scarring. The first outbreak can be more severe and last up to 2 weeks. See a doctor if a sore has not healed after 2 weeks or keeps getting worse.
Is a cold sore the same as herpes?
Yes. Cold sores are caused by herpes simplex virus, usually type 1. Most adults carry the virus. Having cold sores is very common and does not mean you have genital herpes, although HSV-1 can be spread to the genitals through oral sex.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Dermatology: Cold sores: Overview and treatment
- MedlinePlus: Cold sores
- NHS: Cold sores
- World Health Organization: Herpes simplex virus fact sheet
- American Academy of Pediatrics (HealthyChildren.org): Herpes simplex (cold sores)