Confusable diagnoses · PANCE / PANRE

Atopic Dermatitis vs Scabies

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Atopic Dermatitis and Scabies are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Atopic Dermatitis vs Scabies at a glance

  • Atopic Dermatitis: Chronic relapsing pruritic inflammatory dermatosis driven by skin barrier dysfunction and Th2 immune skewing; part of the atopic march.
  • Scabies: Intensely pruritic infestation by Sarcoptes scabiei mite — burrows in web spaces and intensely itchy nocturnal rash; household contacts affected.

Try two board-style questions on Atopic Dermatitis vs Scabies

Real questions from the FirstPassPA bank, with the full explanation. Pick an answer — no signup, no email.

Question 1DermatologyMedium
A 7-year-old boy has chronic intensely pruritic flexural plaques, xerosis, and a history of asthma. Which of the following best explains the pathophysiology?
  • AIgE-mediated contact hypersensitivity
  • BIL-23/IL-17 keratinocyte hyperproliferation
  • CDermatophyte fungal invasion of the skin
  • DBarrier dysfunction with Th2 inflammation
Reveal answer & full explanation
Correct answer: D — Barrier dysfunction with Th2 inflammation
  • AIgE-mediated contact hypersensitivity
  • BIL-23/IL-17 keratinocyte hyperproliferation
  • CDermatophyte fungal invasion of the skin
  • DBarrier dysfunction with Th2 inflammation✓

Why Barrier dysfunction with Th2 inflammation is correct

  • Atopic dermatitis arises from an impaired epidermal barrier (often filaggrin-related) layered with Th2-skewed immune inflammation.
  • The chronic pruritic flexural plaques, dry skin, and personal history of asthma place this squarely in the atopic march.
  • Barrier loss drives water loss and allergen entry, perpetuating the itch-scratch cycle and secondary infection risk.

Why the others are wrong

  • IgE-mediated contact hypersensitivity — Right-immunology-wrong-mechanism trap: allergic contact dermatitis is a delayed T-cell reaction at the contact site, not the barrier-plus-Th2 atopic process.
  • IL-23/IL-17 keratinocyte hyperproliferation — Wrong-pathway trap: the IL-23/Th17 axis drives psoriasis, which typically forms well-demarcated plaques with silvery scale on extensor surfaces, not intensely pruritic flexural eczema with xerosis in an atopic child.
  • Dermatophyte fungal invasion of the skin — Mimic trap: tinea produces annular scaly plaques with central clearing, not chronic atopic flexural disease.
Question 2DermatologyMedium
A 4-year-old boy is brought in for 3 weeks of relentless itching that wakes him at night. He recently started at a crowded daycare, and this is his first such episode. Examination shows scattered erythematous papules and thin gray-white linear tracks in the web spaces between his fingers, and his mother reports that she and his older sister have also begun to itch. Which of the following best explains the pathophysiology of this patient's presentation?
  • AAutoantibodies against epidermal desmoglein causing acantholysis
  • BIgE-mediated mast cell degranulation from an environmental aeroallergen
  • CType IV hypersensitivity to a dermatophyte invading the stratum corneum
  • DDelayed hypersensitivity to a burrowing mite, its eggs, and feces
Reveal answer & full explanation
Correct answer: D — Delayed hypersensitivity to a burrowing mite, its eggs, and feces
  • AAutoantibodies against epidermal desmoglein causing acantholysis
  • BIgE-mediated mast cell degranulation from an environmental aeroallergen
  • CType IV hypersensitivity to a dermatophyte invading the stratum corneum
  • DDelayed hypersensitivity to a burrowing mite, its eggs, and feces✓

Why Delayed hypersensitivity to a burrowing mite, its eggs, and feces is correct

  • Scabies symptoms come from a delayed (type IV) hypersensitivity reaction to Sarcoptes scabiei mites burrowing in the stratum corneum, plus their eggs and scybala (feces).
  • The sensitization lag explains why intense itch may begin weeks after the first infestation.
  • The burrows in finger webs and the immune reaction to mite products are what define the disease.

Why the others are wrong

  • Type IV hypersensitivity to a dermatophyte invading the stratum corneum — that mechanism describes tinea; scabies is caused by a mite, not a fungus, and produces burrows rather than annular scale.
  • IgE-mediated mast cell degranulation from an environmental aeroallergen — that is the immediate-type mechanism of atopic/allergic disease, not the mite-driven delayed reaction with linear burrows.
  • Autoantibodies against epidermal desmoglein causing acantholysis — desmoglein autoantibodies cause pemphigus vulgaris, a blistering autoimmune disease, not a contagious itchy infestation.
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Side-by-side comparison

FeatureAtopic DermatitisScabies
At a glanceChronic relapsing pruritic inflammatory dermatosis driven by skin barrier dysfunction and Th2 immune skewing; part of the atopic march.Intensely pruritic infestation by Sarcoptes scabiei mite — burrows in web spaces and intensely itchy nocturnal rash; household contacts affected.
Classic presentationFlexural eczematous patches with lichenification in a child or adolescent with personal/family atopy.; Intense pruritus — required feature; often worse at night, disrupts sleep; Chronic relapsing course with flares and remissions; Dry skin (xerosis) between flares; Infants (0-2 yrs): erythematous, weeping, crusted patches on cheeks,…Burrows in finger web spaces, flexor wrists, genitalia; intense nocturnal pruritus; multiple affected family members.; Intense generalized pruritus, worse at night, disrupting sleep; Pruritus in close contacts/household members; Onset 4-6 weeks after primary exposure (sensitization period); 1-3 days on reinfestation; Crusted scabies:…
Workup / key labsHanifin and Rajka criteria (3 major + 3 minor) or AAD simplified criteria. Essential features: pruritus + eczematous dermatitis in age-typical distribution + chronic/relapsing course.; Clinical diagnosis — no required labs; Serum total IgE often elevated; allergen-specific IgE or skin-prick testing only if clear allergic trigger…IACS 2020 consensus: confirmed (mites, eggs, or feces on light microscopy of skin samples or on a high-powered imaging device, or mite seen on dermoscopy); clinical (burrows, OR typical lesions on the male genitalia, OR typical lesions in a typical distribution plus 2 history features: itch and positive contact history); suspected…
ImagingNot indicatedNot indicated
First-line treatmentSkin barrier repair: emollient/moisturizer (ceramide-containing, petrolatum-based) applied liberally ≥2x/day and immediately after bathing ('soak and seal'); Lukewarm short baths/showers with non-soap cleanser (e.g., syndet); pat dry; Topical corticosteroid potency tailored to severity and site — hydrocortisone 1-2.5% (low; face, folds,…Topical permethrin 5% cream — apply from neck down (include scalp/face in infants and elderly) overnight (8-14 hours), wash off in morning; REPEAT in 7 days (kills newly hatched larvae); first-line for most patients ≥2 months old; Oral ivermectin 200 mcg/kg PO on day 0 and day 7-14 — first-line alternative; preferred for institutional…

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Full outlines

Atopic Dermatitis (Eczema) Scabies All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.