Both VZV and HSV cause vesicular eruptions — but the clinical context, distribution, and management differ. The distinction changes antiviral choice, duration, and urgency. Dermatomal pain may precede a zoster rash; once the rash appears, start antiviral therapy promptly.
CLINICAL PRINTABLE
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1 · Recognition
- Herpes zoster (shingles): reactivation of latent VZV in the dorsal root ganglion. Presents with prodromal pain, burning, or paresthesia in a dermatomal distribution, followed by a unilateral vesicular rash confined to one or two adjacent dermatomes. Most common in adults over 50 and immunocompromised patients.
- HSV-1 (oral herpes): primary infection typically in childhood. Recurrent episodes present as grouped vesicles on an erythematous base at the vermilion border (herpes labialis). Prodrome of tingling or burning precedes visible lesions by 12–24 hours.
- HSV-2 (genital herpes): primary infection presents with painful vesicles, ulcers, dysuria, and inguinal lymphadenopathy. Recurrent episodes are typically milder. Prodrome of tingling, burning, or shooting pain in the genital/buttock/thigh area precedes lesions.
- Key distinguishing features: shingles — dermatomal, unilateral, does not cross midline, older/immunocompromised host, does not recur in the same dermatome (usually); HSV — recurrent, localized (lips, genitals, buttocks), bilateral involvement possible, any age.
- Zoster sine herpete: dermatomal pain without visible rash. VZV reactivation can cause pain in a dermatomal distribution without skin lesions. Consider in patients with unexplained dermatomal pain, especially in immunocompromised hosts.
2 · Differential / Common Traps
- Diagnosing shingles in a young immunocompetent patient without considering HSV: HSV can present with dermatomal-appearing vesicular eruptions, especially in the sacral dermatomes (S2-S4). Sacral HSV can mimic shingles. PCR testing distinguishes them.
- Missing the prodrome of shingles: dermatomal pain, burning, or paresthesia precedes the rash by 2–5 days. Patients may present with pain alone before visible lesions appear. Consider shingles in any patient with unexplained dermatomal pain, especially if over 50 or immunocompromised.
- Underestimating postherpetic neuralgia (PHN) risk: PHN (persistent pain after rash resolution) occurs in approximately 10–15% of shingles patients overall, but in up to 30–50% of patients over 60. Early antiviral therapy reduces PHN risk. Vaccination (Shingrix) is the most effective prevention.
- Missing herpes zoster ophthalmicus: shingles involving the ophthalmic branch of V1 (forehead, tip of nose — Hutchinson's sign) can involve the eye and cause keratitis, uveitis, and vision loss. Ophthalmology consultation is urgent.
- Inadequate antiviral duration for shingles: valacyclovir 1000 mg TID for 7 days (or acyclovir 800 mg 5x/day for 7 days) is the standard. Shorter courses are not equivalent. Antivirals are most effective when started within 72 hours of rash onset.
3 · Workup and Interpretation
- Clinical diagnosis in most cases — the dermatomal distribution and vesicular morphology are usually sufficient for shingles. HSV is often diagnosed clinically based on recurrent localized vesicular eruptions.
- PCR of vesicle fluid: the most sensitive and specific test for both VZV and HSV. Indicated when the diagnosis is uncertain, presentation is atypical, or the patient is immunocompromised.
- Tzanck smear: rapid bedside test showing multinucleated giant cells — positive for both VZV and HSV but cannot distinguish between them. Largely replaced by PCR.
- Slit-lamp examination: for any shingles involving the V1 dermatome (forehead, tip of nose) — ophthalmology consultation to evaluate for ocular involvement.
- HIV testing: consider in young patients with shingles without other immunocompromising conditions — VZV reactivation in a young patient can be a marker of HIV-related immunosuppression.
4 · Treatment / Management
Herpes zoster (shingles) — antiviral
Valacyclovir 1000 mg TID for 7 days (preferred — better bioavailability). Acyclovir 800 mg 5x/day for 7 days (alternative). Famciclovir 500 mg TID for 7 days (alternative). Start within 72 hours of rash onset for maximum benefit. Antivirals reduce duration, severity, and PHN risk.
Herpes zoster — pain management
Analgesics (acetaminophen, NSAIDs, opioids for severe pain). Gabapentin or pregabalin for neuropathic pain. Tricyclic antidepressants (amitriptyline) for PHN prevention and treatment. Topical lidocaine patches for localized PHN.
HSV-1 (herpes labialis)
Topical acyclovir or penciclovir cream for recurrent herpes labialis — most effective when started at prodrome. Oral valacyclovir 2 g BID for 1 day (single-day therapy) for recurrent episodes. Daily suppressive therapy (valacyclovir 500 mg daily) for frequent recurrences (≥6/year).
HSV-2 (genital herpes)
Primary episode: valacyclovir 1 g BID for 7–10 days. Recurrent episodes: valacyclovir 500 mg BID for 3 days or 1 g daily for 5 days. Suppressive therapy: valacyclovir 500 mg daily (reduces recurrences by 70–80% and reduces transmission risk).
Immunocompromised patients
Higher doses and longer duration of antivirals. IV acyclovir for disseminated or severe disease. Lower threshold for hospitalization. Ophthalmology consultation for any ocular involvement. Consider IV acyclovir for disseminated VZV (widespread vesicular rash beyond one dermatome).
5 · Expected Course / Reassessment
- Shingles rash typically crusts over within 7–10 days and resolves within 2–4 weeks. Antiviral therapy shortens the duration and reduces severity.
- Postherpetic neuralgia (PHN): pain persisting beyond 90 days after rash onset. Occurs in 10–15% overall, up to 30–50% in patients over 60. Early antiviral therapy and Shingrix vaccination reduce risk.
- HSV recurrences typically decrease in frequency over time. Suppressive therapy significantly reduces recurrence frequency and transmission risk.
- Shingrix vaccination (two-dose series) is 90%+ effective at preventing shingles and PHN in adults over 50. Recommended even in patients with prior shingles.
6 · Escalation
- Herpes zoster ophthalmicus (V1 involvement, Hutchinson's sign) — urgent ophthalmology consultation, IV acyclovir if severe.
- Disseminated zoster (vesicles beyond one dermatome, especially in immunocompromised) — IV acyclovir, hospitalization.
- Ramsay Hunt syndrome (VZV reactivation in geniculate ganglion — ear pain, facial palsy, vesicles in ear canal) — antiviral + corticosteroids, ENT/neurology consultation.
- Eczema herpeticum (HSV dissemination in atopic dermatitis) — IV acyclovir, hospitalization, dermatology consultation.
Apply It · Patient Cases
CASE 1
A 67-year-old presents with 3 days of burning pain on the right chest followed by a unilateral vesicular rash in a T5 dermatomal distribution. Herpes zoster is diagnosed. Valacyclovir 1000 mg TID for 7 days is started. Gabapentin is added for neuropathic pain. She is counseled about PHN risk and Shingrix vaccination after the acute episode resolves.
CASE 2
A 28-year-old presents with recurrent grouped vesicles on the right buttock, preceded by tingling. This is the fourth episode in 18 months. Recurrent sacral HSV-2 is diagnosed. Suppressive valacyclovir 500 mg daily is started to reduce recurrence frequency and transmission risk.
NOW CHANGE ONE DETAIL
Same patient as Case 1, but the rash involves the forehead and the tip of the nose (Hutchinson's sign). Herpes zoster ophthalmicus is suspected. Ophthalmology is consulted urgently — slit-lamp examination reveals corneal involvement. IV acyclovir is started and she is admitted for close monitoring.
Bottom Line
Dermatomal pain may precede a zoster rash. Once the rash appears, start antiviral therapy promptly, ideally within 72 hours. Hutchinson's sign (tip of nose) means ophthalmology consultation today.
EVIDENCE & REFERENCES
- Dworkin RH, et al. Recommendations for the management of herpes zoster. Clin Infect Dis. 2007;44(Suppl 1):S1–26. doi:10.1086/510206
- Gnann JW Jr, Whitley RJ. Clinical practice. Herpes zoster. N Engl J Med. 2002;347(5):340–346. doi:10.1056/NEJMcp013211
- Workowski KA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1–187. doi:10.15585/mmwr.rr7004a1