Cold Sores

Cold sores (also called fever blisters) are small, painful fluid-filled blisters that appear on or around the lips and the edge of the mouth. They are caused by the herpes simplex virus — usually HSV-1. Once infected, the virus stays in the body and can reactivate throughout life, usually triggered by stress, illness, sun exposure, or a fever.

Symptoms

Outbreaks usually follow a pattern:

• Tingling or itching 1-2 days before the blister appears
• Blisters — small, painful, fluid-filled, often in clusters around the lips
• Break and ooze — blisters break, forming a shallow open sore that may weep fluid
• Crusting over — a yellow-brown crust forms, then peels off as the sore heals
• Complete healing in 1-2 weeks

The first outbreak after initial infection can be severe — multiple painful sores, fever, swollen glands, body aches — especially in children. Later recurrences are usually milder and briefer.

How it spreads

• Direct contact with a sore — kissing, sharing utensils, sharing lip balm, oral sex
• Most contagious when the sore is weeping or crusted
• Virus can shed even without a visible sore
• Avoid contact with babies and people with weakened immunity during an active sore
• Don't touch the sore — virus can spread to eyes or fingers (painful whitlow)

Treatment

• Topical antiviral cream — applied at the very first sign of tingling; less effective once a blister is established
• Oral antiviral medicines — for severe or frequent outbreaks; reduce severity and duration
• Paracetamol for pain
• Cool, damp cloth on the sore can soothe
• Lip balm with SPF — to protect from UV-triggered recurrences
• Don't pick the scab — slows healing and can cause scarring

When to see a doctor

• Very frequent outbreaks (more than 6 a year) — consider suppressive antivirals
• Severe first outbreak
• Cold sores in a person with weakened immunity (HIV, chemotherapy)
• Sores that spread to the eye — can threaten vision; urgent ophthalmology review
• Sores that persist for more than 2 weeks
• Any signs of secondary bacterial infection — spreading redness, significant pus, fever

Reducing recurrences

• Manage stress
• Protect lips from sun — use SPF lip balm
• Get enough sleep
• Stay generally well — eat well, manage illness early
• Daily suppressive antivirals for people with frequent severe outbreaks