She has Herpes zoster. The presentation of localised pain, malaise and rash is characteristic, but is surprisingly often misdiagnosed. There are small grouped vesicles on an inflamed base in a dermatomal distribution.

No investigations are necessary in most patients as the diagnosis is made clinically. In doubtful or unusual cases, herpes zoster can be confirmed by tissue culture of scrapings from a de-roofed blister.

Treatment guidelines in the Pharmaceutical Schedule recommend oral aciclovir 800mg daily five times daily for seven days in the following circumstances:

• Ophthalmic zoster
• Immunocompromised patients
• If rash present for <3 days in patients over 50 with significant pain.

Valaciclovir and famciclovir are no longer available in New Zealand.

In addition, analgesics such as paracetamol, codeine phosphate, narcotics or amitripytline/nortripyline may be prescribed. Soothing antiseptic topical applications may be helpful.

The use of systemic corticosteroids is controversial and is not currently recommended.