This is usually caused by the herpes simplex virus type 1 (HSV-1), but occasionally HSV-2, more often associated with genital herpes simplex. The patient presents with a vesicular eruption on the lips, and there may also be lesions within the mouth. The vesicles break down and leave ulcers that heal over in the following seven to 10 days. The regional lymph glands can be enlarged and the patient might be feverish. The condition can be more problematic in the immunocompromised or pregnant women, for whom specialist advice is required. Some patients will be aware of itching, paraesthesia and pain for some hours before the eruption occurs. Some of those suffer repeated episodes of this condition and might be able to minimise the symptoms if they recognise them, and apply a topical antiviral preparation to the lips five times daily for about a week. Once the vesicles have appeared, this provides no benefit. Paracetamol or ibuprofen can be offered to ease the pain. Episodes may be triggered by sun exposure, trauma, menstruation or tiredness.