Herpes Simplex

Skin Lesion: Recurrent clusters of small, grouped vesicles on an erythematous base. Lesions progress to painful, shallow erosions and eventually crust over.

Classic Clues:

• Prodrome: Tingling, itching, or burning sensation at the site 6–24 hours before vesicles appear.
• Recurrence: Tendency to recur in the exact same anatomical location (triggered by stress, illness, or UV light).
• Types: HSV-1 is typically orolabial (Cold Sores); HSV-2 is typically genital (though crossover is common).

Aphthous Ulcer (Canker Sore)

• The Clue: Solitary or few painful ulcers with a yellow-white necrotic center and a halo of redness, found on non-keratinized mucosa (inner lip, buccal mucosa).
• Vs HSV: HSV usually starts as vesicles (blisters); Aphthous ulcers are always flat/depressed and never vesicular. HSV also favors keratinized skin (outer lip).

Primary Syphilis (Chancre)

• The Clue: A solitary, painless, indurated (firm) ulcer with a clean base.
• Vs HSV: Herpes lesions are exquisitely painful and usually multiple/clustered; a Syphilitic chancre is classically painless and solitary.

🚨 Urgent Referral or Monitoring if:

• Eczema Herpeticum: Widespread HSV infection in patients with Atopic Dermatitis (Dermatological Emergency).
• Herpetic Whitlow: HSV infection of the finger (painful vesicles on the fingertip).
• Ocular Involvement: Dendritic ulcers on the cornea (Urgent Ophthalmology review).
• Neonatal Herpes: High mortality risk; urgent pediatric admission.

Antiviral (Optimal <72H):

• Acyclovir: 200mg 5 times daily for 5-10 days.
• Valacyclovir: 500mg BD (1g BD if immunocompromised) for 7–10 days.
• Famciclovir: 250mg TDS (500mg TDS if immunocompromised) for 7–10 days.
• Topical Acyclovir 5% Cream (Every 4 hours).

⚠️ Clinical Pearl: For genital herpes, inform the patient that viral shedding can occur even when no lesions are visible. Asymptomatic transmission is a major driver of spread.