- Clinical science
Shingles (herpes zoster) is a dermatomal rash with painful blistering that is caused by the reactivation of the varicella zoster virus (VZV). The initial infection with VZV usually occurs early in life, presenting as chickenpox (varicella), after which the virus remains dormant in the dorsal root ganglia. Immunocompromised individuals are at increased risk of VZV reactivation. Shingles is generally a clinical diagnosis, although further testing (e.g., PCR) may be indicated in unclear cases. Treatment with antiviral drugs, such as acyclovir, is usually effective. Potential complications include encephalitis and, particularly in the elderly population, painful postherpetic neuralgia. VZV may also affect the cranial nerves. Involvement of the trigeminal nerve may cause visual impairment up to blindness (herpes zoster opthalmicus), while involvement of the facial and vestibulocochlear nerves can cause facial paralysis and hearing loss (herpes zoster oticus). These presentations, in particular, require urgent medical attention to prevent serious complications.
- Causative pathogen: varicella zoster virus (HHV-3)
- Immunocompromised individuals are at particular risk of VZV reactivation and may be caused by:
- Primary infection (chickenpox): respiratory transmission → VZV inoculates the lymphoid tissue of the nasopharynx and, subsequently, regional lymphoid tissue → viremia + chickenpox → recovery from chickenpox, but virus remains dormant in dorsal root ganglia (unless reactivated → recurrent infection)
- Reactivation (shingles): VZV reactivated (e.g., due to immunocompromise) → virus replicates in the dorsal root ganglia → travels through peripheral sensory nerves to the skin → shingles (less contagious than primary infection)
Pain and rash in a dermatomal distribution, typically affecting 1–3 dermatomes on one side of the body
- Most commonly affects the cervical, trigeminal, thoracic, and lumbar dermatomes 
- Usually described as “burning”, “throbbing”, or “stabbing”
- may occur
- Erythematous maculopapular rash that quickly evolves into vesicular lesions
- Additional symptoms may be present: 
Disseminated herpes zoster: herpes zoster characterized by > 20 extradermatomal lesions, involvement of ≥ 3 dermatomes, and/or visceral organ involvement. 
- Typically only seen in patients who are immunocompromised.
- Immunocompromised individuals may have an atypical presentation (e.g., no rash, recurrent herpes zoster, or disseminated zoster ).
- Definition: reactivation of VZV in the ophthalmic division of the trigeminal nerve
- Fever and skin symptoms as in shingles (see “Clinical features” above)
- Involvement of the ophthalmic nerve: reduced corneal sensitivity with severe pain in the innervated regions (forehead, bridge and tip of the nose)
- Involvement of the nasociliary nerve:
- Definition: : reactivation of VZV in the geniculate ganglion, affecting the seventh (facial) and eighth (vestibulocochlear) cranial nerves (also known as Ramsay Hunt syndrome)
- Clinical features
- Diagnosis: tone audiometry
Clinical presentation is usually sufficient for a diagnosis. 
- PCR of VZV DNA 
Additional tests to consider 
- Serologic assay of VZV (IgM and IgG): can be used to identify active or passive immunity and diagnose primary VZV infection 
- Direct fluorescent antibody (DFA) of skin scrapings: not routinely recommended because it has a low sensitivity
- Tzanck test of skin vesicles
- Patients with recurrent herpes zoster infection or disseminated zoster: Consider evaluation for underlying malignancies, immunosuppression, or other causes (e.g., herpes simplex).
Antiviral therapy 
Antiviral therapy speeds up the resolution of lesions, reduces viral shedding, reduces the formation of new lesions, and decreases pain. Antiviral therapy is most effective if administered within approx. 72 hours or while new lesions are erupting.
- Indications 
Antiviral therapy should be initiated as early as possible since the effectiveness of antiviral treatment decreases as the disease progresses.
Supportive care 
Anti-inflammatory and analgesic therapy 
- For mild pain, consider one or more of the following: 
- For moderate to severe pain, add one of the following: 
- For refractory or severe pain: Consider pain specialist consultation for possible neural blockade. 
Admission criteria and disposition 
- Consider hospitalization if:
- The patient is immunocompromised
- Symptoms are atypical and/or severe (e.g., refractory or severe pain and rash, involvement of more than two dermatomes, disseminated zoster)
- There are complications (e.g., signs of myelitis, meningoencephalitis, ophthalmic involvement, or severe bacterial superinfection)
- Consider the following specialist consultations:
- Initiate antiviral therapy.
- Pain management and supportive care
- Consider adjunctive corticosteroids.
- Admit to the hospital and administer IV antivirals if there are signs of complicated herpes zoster, immunocompromised state, or disseminated zoster.
- Consider specialist consultation.
- Immunization with zoster vaccine
Postherpetic neuralgia 
- Definition: chronic neuropathic pain persisting for at least three months in the area previously affected by the rash
- Most common complication (occurs in 10–20% of overall herpes zoster cases)
- Strong association with age 
Risk factors 
- Age > 50 years
- Severe infection
- Ocular involvement
- Clinical features 
- The initial choice of analgesics should be guided by side-effect profiles, the potential for drug interactions, and patient comorbidities.
- One of the following tricyclic antidepressants: 
- One of the following anticonvulsants: 
- Topical treatments 
- Topical capsaicin patch or capsaicin cream 
- Lidocaine patch 
- Opioids 
- Interventional pain therapy: Consider intrathecal glucocorticoid injections and/or neural blockade for severe cases.
- Prognosis: Pain typically continues to decrease over the first year but may last for months to years. 
- Risk factors 
- Clinical features 
- Treatment 
Additional complications 
- Cranial nerve involvement
- CNS involvement
- Ocular complications of herpes zoster 
We list the most important complications. The selection is not exhaustive.
Live varicella vaccine is recommended for all healthy people with no evidence of immunity to varicella.
- Children: 1st dose at 12–15 months, 2nd dose at 4–6 years (see )
- Adolescents (≥ 13 years of age) and adults with no evidence of immunity: 2 doses 4–8 weeks apart
- Contraindications include immunosuppression, known allergy to the vaccine, pregnancy, and transfusion of blood products in the last year.
- Live varicella vaccine is recommended for all healthy people with no evidence of immunity to varicella.
- Shingles: Herpes zoster immunization is generally recommended for individuals ≥ 50 years of age (regardless of previous chickenpox status).