Herpes simplex
Also called HSV, cold sores, herpes labialis, genital herpes
Grouped vesicles on an erythematous base that break into punched-out erosions and come back to the same address: that recurrence, announced by a prodrome of tingling, is the diagnosis. The dangerous forms are ocular disease and HSV loose on atopic skin.
How it looks
A cluster of uniform vesicles on an erythematous base at the vermilion border, several already broken into punched-out crusted erosions.
Rose is the lesion, grey the pattern the lesions make, green where on the body it lives.
Across skin tones
The erythematous base reads violaceous or is easily missed in deeply pigmented skin, and lesions resolve with noticeable post-inflammatory pigment change; the grouped monomorphic vesicles and the recurrence history carry the diagnosis.
Don't miss
Punched-out erosions marching across an atopic child's eczema with fever is eczema herpeticum: systemic antivirals now, ophthalmology if near the eye, and stop the topical steroid over it.
Forms & variants
Orolabial herpes (cold sores)
Grouped vesicles at the vermilion border heralded by tingling; recurrences pick the same spot, triggered by sun, illness, and stress.
Genital herpes
Painful grouped vesicles and erosions with a severe, systemic first episode and milder recurrences; suppression exists and disclosure counselling matters as much as the prescription.
Eczema herpeticum
HSV sweeping across atopic skin: abrupt monomorphic punched-out erosions, fever, and pain replacing itch. A dermatologic emergency treated with systemic antivirals, never with more topical steroid.
Herpetic whitlow
HSV of the fingertip, vesicles on a painful red digit; classically misdiagnosed as bacterial and incised, which it should not be.
Symptoms & course
- Tingling or burning prodrome before anything is visible
- Painful vesicles then erosions over 7-10 days
- First episodes are systemic; recurrences are local
Diagnostic approach
- Clinical for classic recurrences
- Swab vesicle fluid for PCR when it matters: atypical sites, immunocompromise, eczema herpeticum, genital first episodes
Differential, and how to separate them
- Impetigo
Favours it: Honey-coloured perioral crusting
Against it: Impetigo spreads and crosses midlines; HSV clusters at one site it has used before
- Herpes zoster
Favours it: Grouped vesicles on red skin
Against it: Zoster is a dermatomal band that stops at the midline and rarely recurs; HSV is a small recurring cluster
- Contact dermatitis
Favours it: Acute vesicles on the lips or face
Against it: Contact reactions itch rather than hurt, follow exposure geometry, and lack the prodrome-recurrence rhythm
Management principles
- Early oral antivirals shorten episodes; start at the prodrome for recurrences
- Daily suppression for frequent or disclosure-sensitive recurrences
- Systemic antivirals plus urgent review for ocular disease or eczema herpeticum
Clinical pearl: Ask 'has this exact spot blistered before?'; a yes nearly closes the case, because HSV is the only common rash with a fixed home address.
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