About cold sores
Cold sores (herpes labialis) are caused by the herpes simplex virus (most commonly HSV-1), which establishes a lifelong infection after the first exposure. The virus stays dormant in nerve cells and reactivates intermittently to produce the characteristic blisters on or around the lips. Most adults in Ireland — around 60–80% — carry the virus, though not everyone has visible outbreaks. While usually harmless, cold sores can be uncomfortable and recur predictably with specific triggers.
Symptoms and signs
- Tingling, burning, or itching 12–24 hours before any visible lesion (the "prodrome")
- Cluster of small fluid-filled blisters, usually on the lip or around the mouth
- Blisters burst, weep, then form a yellow-brown crust
- Heals over 7–10 days without scarring (most cases)
- Recurrence at the same site is typical
- First outbreak may include fever, swollen glands, and more widespread mouth ulcers
Causes and common triggers
Triggers for HSV-1 reactivation per NICE CKS: sun exposure (UV light), other illness or fever, fatigue, stress, menstruation, immunosuppression, and local trauma (dental work, lip injury). Recurrence pattern varies widely — some people have 1–2 outbreaks a year, others have monthly recurrence.
When to seek help — and when it's urgent
An Online Doctor consultation is appropriate for typical recurrent cold sores, especially for prescription antiviral treatment to start early. Seek urgent care for any of: cold sore near the eye or any eye symptoms (risk of herpes keratitis — sight-threatening); widespread painful blisters over the face or body; cold sore in someone with eczema (risk of eczema herpeticum — needs urgent treatment); severe outbreak with high fever and feeling generally unwell; immunocompromised patients (cancer treatment, organ transplant, HIV, certain medications); newborn baby exposure (specific neonatal pathway).
Treatment options
Per NICE and ICGP guidance:
- Topical aciclovir cream — applied at the first sign of tingling (prodrome); most effective when started very early
- Oral antiviral therapy (aciclovir, valaciclovir, famciclovir) — for more severe outbreaks, frequent recurrence, or immunocompromised patients
- Suppressive therapy — continuous low-dose oral antiviral for very frequent recurrences (≥6/year); usually after specialist review
- Symptomatic relief — paracetamol or ibuprofen for pain; barrier creams (petroleum jelly) over scabs
- Avoid topical corticosteroids on cold sores (worsens viral spread)
Self-care and preventing spread
Apply sun protection on lips (SPF 30+ lip balm) — UV is a major trigger. Don't share lip balm, towels, or drinks during an outbreak. Avoid kissing or oral sex during outbreaks. Wash hands after touching the cold sore. Don't touch your eyes after touching the cold sore. Don't pick the crusts — let them heal naturally. Soft, cool foods reduce discomfort.
Frequently asked questions
Am I infectious between outbreaks?
HSV-1 can be shed asymptomatically (without visible lesions), but transmission risk is much higher during active outbreaks. The virus is most contagious from the tingle phase through to fully scabbed lesions.
Can cold sores be cured?
No — the virus persists lifelong in nerve cells. Treatment shortens individual outbreaks and reduces severity but doesn't eliminate the underlying infection. Some people find recurrence becomes less frequent over years.
Is HSV-1 the same as genital herpes?
HSV-1 typically causes oral herpes (cold sores). HSV-2 typically causes genital herpes. However, HSV-1 can cause genital infection through oral-genital contact, and HSV-2 can occasionally cause oral lesions. Both are managed similarly.
Can I get aciclovir online?
Yes — for confirmed recurrent cold sores in adults, an Online Doctor can prescribe topical aciclovir cream or oral antiviral treatment if appropriate. Suppressive therapy or unusual presentations may warrant in-person assessment first.
Sources: HSE.ie, NICE CKS Herpes Simplex (Oral), ICGP. General information only.