Is it shingles?

Many patients describe a prodromal phase with abnormal skin sensations and pain in the affected dermatome (as mentioned, an area of skin served by an individual nerve root).

The pain can be described as burning, stabbing, or throbbing, can be intermittent or constant, and may be so severe it interferes with sleep and quality of life. Headache, photophobia, malaise and fever (less common) may also occur as part
of the prodromal phase.

If patients are seen at this time, it can be difficult to be sure of the cause in the absence of a rash. A good policy is to ask the patient to return straight away if a rash follows. Some GPs will start oral antiviral therapy if they believe shingles is imminent (although this use is controversial).

Within two to three days (sometimes longer), a rash typically appears in a dermatomal distribution. The rash starts as maculopapular (red, raised) lesions, then develops into clusters of vesicles (small blisters), with new vesicles continuing to form over three to five days, before resolving over seven to 10 days. The vesicles burst and this releases varicella zoster virus.

The rash is usually itchy and tingly, and can be very painful. Unlike most other rashes, it is unilateral (either on the left or right) and does not usually cross the midline of the body, but there may occasionally be a slight spread to the other side around the skin over the spine. 

Healing of the affected skin occurs over two to four weeks and the damage from infection can cause scarring and permanent pigmentation.

Most cases of shingles involve the thorax, trunk and abdomen. A problem with diagnosis is the extent to which the rash can vary. This is why PGDs for community pharmacy supply of aciclovir are very specific about the scope of the infection and which patients can be treated.

The rash may be atypical in certain groups –for example, older people (in whom the rash may not be vesicular) and in immunocompromised patients, in whom the rash may be severe or long-lasting. Symptoms can also be more widespread for immunocompromised people and affect multiple dermatomes.

Although pain is a common feature, some people, particularly younger patients, get little discomfort. If there is doubt over the diagnosis, these cases should be referred to primary care, alongside those in whom there are red flags.