Cold sores are a very common viral condition caused by the herpes simplex virus (HSV). Once someone is exposed to the virus, it stays dormant in the body and can reactivate during periods of illness, stress, fatigue, or reduced immunity.

This is why many people experience cold sores during or after flu, viral infections, or times of intense physical or emotional stress. If you’re currently unwell with flu-like symptoms, you may find our guide on flu symptoms, recovery and vaccination helpful alongside cold sore management.

What Do Cold Sores Look and Feel Like?

Cold sores usually follow a recognisable pattern:

Tingling, burning or itching around the lips or mouth
Development of small fluid-filled blisters
Weeping, crusting and scabbing
Healing over 7–10 days

They most commonly appear on the lips, but can also affect the nose or surrounding skin.

What Triggers Cold Sores?

Common triggers include:

Viral illness (such as flu or severe colds)
Fever
Stress
Sun exposure
Hormonal changes
Reduced immunity
Fatigue

If you find your cold sores are linked to frequent illness, it may be worth reviewing your overall immune health and seasonal protection, including flu vaccination during winter months.

Cold sore treatment options

At the first sign of tingling, antiviral creams can help shorten the outbreak if used promptly.
These are most effective when started within the first 24 hours.
You can also get occlusive creams which can help to reduce the risk of spreading the virus, and reduce the risk of bacterial infection in the wound.
For more severe, painful, frequent or prolonged outbreaks, oral antiviral tablets may be more effective than creams alone.
Important to know:
- ✅ Tablets require a prescription
- ✅ They cannot legally be supplied without a clinical assessment
- ✅ They work best when started early in the outbreak
- ✅ They are often used for:
  - Frequent recurrences
  - Very painful lesions
  - Immunocompromised patients
  - Cold sores triggered by illness such as flu
At Pharmacy Clinic Edinburgh, you can access a private online consultation to assess suitability for prescription treatment without long NHS waits. See more here.