Overview
Cold sores are small blisters that develop on or around the lips, caused by the herpes simplex virus type 1 (HSV-1). After the first infection, the virus lives permanently in nerve cells. It reactivates periodically to cause the familiar blister outbreaks.
How common is it?
Around 67% of people under 50 worldwide are infected with HSV-1. Most catch it in childhood through contact with an infected person, often without any symptoms at the time.
Causes and risk factors
HSV-1 is acquired by close contact with the lips, saliva, or skin of an infected person, typically through kissing or sharing utensils. The virus travels to nerve cells where it stays dormant between outbreaks.
Common risk factors
- Close contact with someone with an active cold sore
- Sun exposure (UV light triggers reactivation)
- Fever or illness
- Stress or emotional upset
- Hormonal changes including menstruation
- Immunosuppression from medication or illness
Symptoms
- Tingling, itching, or burning on the lip before a blister appears
- Small fluid-filled blisters on or near the lips
- Blisters that burst, crust over, and heal over 7 to 10 days
- Pain or tenderness at the site
- First infection may cause sore mouth, swollen gums, and fever in children
When to see a doctor
See a doctor if cold sores are spreading to the eye (which can damage sight), occurring very frequently, or if you are immunosuppressed. Very large, painful, or persistent sores need assessment.
Diagnosis
Usually diagnosed by appearance alone. Swabs of blister fluid can confirm HSV-1 in atypical cases or to distinguish from other infections.
Treatments
Antiviral cream (aciclovir)
Available over the counter. Applied at the earliest tingle or blister stage, it can shorten the outbreak by a day or two. Needs to be applied frequently.
Oral antiviral medication
Aciclovir, valaciclovir tablets are prescribed for frequent outbreaks or severe episodes. Daily suppressive therapy significantly reduces outbreak frequency.
Pain relief and lip balm
Paracetamol or ibuprofen for discomfort. Lip balm with sun protection prevents UV-triggered reactivation.
Self-care and lifestyle
- Apply SPF lip balm outdoors to reduce UV-triggered outbreaks
- Do not kiss anyone, share utensils, or engage in oral sex during an active outbreak
- Wash hands after touching the blister to avoid spreading the virus
- Manage stress and get adequate sleep to reduce outbreak frequency
Prevention
Avoid kissing people with active cold sores and do not share cups or lip products. There is no vaccine currently available. Once infected, the virus cannot be eliminated.