Scabies

Skin Lesion: Extremely pruritic papules, vesicles, and the pathognomonic Burrow (wavy, grey-white thread-like line). Secondary changes include excoriations, eczematisation, and crusting from infection.

Age-Specific Distribution:

• Adults (The Circle of Hebra): Rash is localized to skin folds—finger webs, flexor of wrists, axillae, umbilicus, areola, and genitalia. The face and scalp are spared.
• Infants & Children: Distribution is often generalized. Frequently involves the face, scalp, palms, and soles.
• Nocturnal Predilection: Itch is significantly worse at night.

Bedbug Bites (Cimicosis)

• The Clue: "Breakfast, Lunch, Dinner" pattern (3 or more bites in a linear row).
• Vs Scabies: Bites occur on exposed skin while sleeping (neck, arms, back). Scabies favors skin folds and finger webs.

Flea Bites

• The Clue: Small, itchy red papules with a central puncture (punctum).
• Vs Scabies: Typically restricted to the ankles and lower legs. Scabies is more widespread and involves the genitalia/finger webs.

Eradication Strategy:

• Permethrin 5% Cream: Apply from neck-to-toe. Leave on for 8-12 hours then wash off. MUST repeat in 7 days to kill newly hatched mites. [Safe in pregnancy].
• Environmental: Treat all household contacts simultaneously. Wash bedding and clothing in hot water (>60°C).

Symptomatic Treatment:

• Cetirizine 10mg OD.
  [Child: 0.25mg/kg OD]
• Piriton 4mg ON/TDS.
  [Child: 0.1mg/kg ON/TDS]
• Calamine Lotion

⚠️ Clinical Pearl: Post-scabietic itch can last for 2-4 weeks due to hypersensitivity; this is not necessarily a sign of treatment failure.

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