ConditionSkin, hair & nails
Oral Herpes (Cold Sores)
Oral herpes is an infection of the mouth area with the herpes simplex virus, usually type 1 (HSV-1). After the first infection, often in childhood, the virus stays dormant in nerve cells for life and can reactivate to cause cold sores: clusters of small, painful blisters on or around the lips that crust and heal in 7 to 10 days. Roughly half of US adults under 50 carry HSV-1. It spreads by kissing and close contact. Antiviral medicines shorten outbreaks and reduce recurrences.
Also called: Cold sores, fever blisters, herpes labialis, HSV-1 infection, herpetic gingivostomatitis (first infection in children)
At a glance
- Cause
- Herpes simplex virus, mostly HSV-1; sometimes HSV-2.
- How common
- About half of US adults aged 14 to 49 have HSV-1; many never have symptoms.
- First infection
- Often in childhood; can cause painful mouth sores and fever (gingivostomatitis).
- Recurrences
- Tingling, then blisters on the lip border that crust and heal in 7 to 10 days.
- Spread
- Kissing, sharing utensils or lip products, oral sex; even without visible sores.
- Treatment
- Antiviral tablets or creams; daily antivirals for frequent outbreaks.
When to get help
Call 911 or go to the ER
- A newborn or baby under 6 weeks with blisters, fever, poor feeding or unusual sleepiness, or exposure to someone with an active cold sore: call 911 or go to the ER
- Severe headache, confusion, seizures or fever with a cold sore (possible herpes encephalitis, rare)
See a doctor within a day or two
- A painful red eye, light sensitivity or blurred vision with a cold sore (possible herpes eye infection)
- Widespread blisters on skin affected by eczema (eczema herpeticum)
- A child with mouth sores who is refusing to drink or has very few wet diapers
- Cold sores in someone with a weakened immune system, or sores lasting more than 2 weeks
Book a routine appointment
- Frequent outbreaks (6 or more a year) or very painful outbreaks
- A painful sore on a finger after touching a cold sore (herpetic whitlow)
Usually safe to manage at home
- A typical cold sore on the lip in a healthy adult or older child
How oral herpes works
HSV enters through small breaks in the skin or mucous membranes. After the first infection, the virus travels along nerves to a cluster of nerve cells (the trigeminal ganglion) and stays there dormant for life. From time to time, it travels back down the nerve to the skin and causes a cold sore. Between outbreaks, it can still be shed silently in saliva.
HSV-1 traditionally caused oral herpes and HSV-2 genital herpes, but HSV-1 now causes a large share of new genital herpes cases through oral sex.
Symptoms
First (primary) infection
Many people have no symptoms. Others, especially young children, develop herpetic gingivostomatitis:
- fever, irritability and swollen glands in the neck
- many painful sores on the gums, tongue, inside the cheeks and lips
- red, swollen, bleeding gums
- drooling and refusal to eat or drink
It lasts about 1 to 2 weeks. Dehydration is the main risk.
Recurrent outbreaks (cold sores)
- Prodrome: tingling, itching or burning at the lip edge, often 6 to 24 hours before blisters.
- Blisters: small fluid-filled blisters in a cluster on or near the lip border (vermilion).
- Ulcer and crust: blisters burst, ooze and form a yellowish crust.
- Healing: usually within 7 to 10 days, without scarring.
Recurrences tend to be milder than the first infection and become less frequent over time.
Triggers
- colds, flu and fever (hence "fever blisters")
- sunlight and wind
- stress and fatigue
- menstrual periods
- injury to the lips, dental work or cosmetic procedures
- weakened immunity
How it spreads
- direct contact with a cold sore or infected saliva: kissing, sharing cups, utensils, razors, towels or lip balm
- oral sex, which can spread HSV-1 to the genitals
- asymptomatic shedding: the virus can spread even without a visible sore, though risk is highest when sores are present
- to other parts of the body: the eyes, fingers (herpetic whitlow) or eczema-affected skin
Avoid kissing babies if you have a cold sore. Newborns are at risk of serious, widespread infection.
Oral herpes vs other mouth sores
| Oral herpes | Canker sores | Impetigo | |
|---|---|---|---|
| Location | Outside the mouth on the lip border (primary infection can be inside) | Inside the mouth on soft tissue | Around the nose and mouth |
| Appearance | Clusters of blisters that crust | Round white or yellow ulcers with red rim | Honey-colored crusts |
| Contagious | Yes | No | Yes |
| Cause | Virus | Unknown; stress, minor injury | Bacteria |
Diagnosis
Cold sores are usually diagnosed by their appearance and history. If unclear, a swab of a fresh blister can be tested by PCR. Blood antibody tests show past infection but cannot tell where the infection is, and are not routinely recommended for people without symptoms.
Treatment
There is no cure, but treatment shortens outbreaks and reduces recurrences.
Antiviral medicines
- Oral antivirals (acyclovir, valacyclovir, famciclovir) work best when started at the first tingle. Short single-day or 1 to 2 day courses are effective for adults.
- Suppressive therapy: daily antivirals for people with frequent, severe or disruptive outbreaks, or before known triggers such as dental work or skiing.
- Topical treatments: docosanol cream (over the counter) or prescription antiviral creams modestly shorten healing if applied early.
Self-care
- cold compresses for pain and swelling
- acetaminophen (paracetamol) or ibuprofen for pain; follow the label dose and do not give aspirin to children or teenagers
- petroleum jelly or lip balm to prevent cracking
- in children with gingivostomatitis: cool drinks, popsicles, soft foods; doctors may prescribe acyclovir if started early
Prevention
- use SPF 30 or higher lip balm outdoors
- avoid touching, picking or squeezing sores; wash hands after touching
- do not share items that touch the mouth during outbreaks
- avoid kissing and oral sex when sores or prodrome symptoms are present
- discuss suppressive antivirals for frequent outbreaks
Frequently asked questions
How is oral herpes spread?
It spreads through direct contact with the virus, mainly by kissing, sharing utensils, cups or lip products, and oral sex. It is most contagious when sores are present, but can also spread when there are no visible symptoms.
What does a first oral herpes outbreak look like?
In children, a first infection often causes fever, swollen gums and many painful sores inside and around the mouth lasting 1 to 2 weeks. In adults, it may cause a severe cold sore, sore throat and swollen glands, or no symptoms at all.
How long do cold sores last?
Most cold sores heal within 7 to 10 days. Starting antiviral medicine at the first tingle can shorten an outbreak by a day or two and sometimes stop blisters forming.
Can oral herpes be cured?
No. The virus stays in the body for life. However, outbreaks usually become less frequent over time, and antiviral medicines effectively shorten outbreaks and, when taken daily, reduce how often they occur.
Can you get genital herpes from a cold sore?
Yes. HSV-1 from a cold sore can be passed to the genitals through oral sex, and it is now a common cause of genital herpes. Avoid oral sex when you have a cold sore or feel the tingling that comes before one.
Sources
This guide was written from current patient and clinical guidance, including:
- CDC: About genital herpes and HSV-1
- World Health Organization: Herpes simplex virus fact sheet
- American Academy of Dermatology: Herpes simplex, diagnosis and treatment
- MedlinePlus: Oral herpes
- NHS: Cold sores
- National Center for Health Statistics: Herpes simplex virus prevalence among adults