Atopic Dermatitis and Seborrheic Dermatitis 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 Seborrheic Dermatitis at a glance
Atopic Dermatitis: Chronic relapsing pruritic inflammatory dermatosis driven by skin barrier dysfunction and Th2 immune skewing; part of the atopic march.
Seborrheic Dermatitis: Chronic relapsing dermatitis of sebum-rich areas associated with Malassezia overgrowth; manifests as cradle cap (infants) and dandruff (adults).
Try two board-style questions on Atopic Dermatitis vs Seborrheic Dermatitis
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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 34-year-old man presents with a 6-month history of a mildly itchy, flaky scalp that worsens during the winter. He has tried an over-the-counter moisturizing shampoo without relief. He has no other medical problems and takes no medications. On examination there is fine greasy yellow scale on an erythematous base across the scalp, with similar scaling in the eyebrows and nasolabial folds. The remainder of the skin exam is unremarkable. Which of the following is the most appropriate initial therapy?
ACalcipotriene 0.005% solution
BKetoconazole 2% topical shampoo
CClobetasol 0.05% scalp solution
DHydrocortisone 1% topical lotion
Reveal answer & full explanation
Correct answer: B — Ketoconazole 2% topical shampoo
ACalcipotriene 0.005% solution
BKetoconazole 2% topical shampoo✓
CClobetasol 0.05% scalp solution
DHydrocortisone 1% topical lotion
Why Ketoconazole 2% topical shampoo is correct
Mild-to-moderate adult scalp seborrheic dermatitis is treated first-line with an antifungal shampoo (ketoconazole 2%, selenium sulfide 2.5%, zinc pyrithione, or ciclopirox), lathered and left on about 5 minutes 2-3 times per week.
These agents target Malassezia yeast, which metabolizes sebum into irritating free fatty acids that drive the inflammatory response.
The greasy yellow scale in a sebaceous distribution (scalp, eyebrows, nasolabial folds) is classic, and antifungal shampoo is the appropriate, low-risk starting point.
Why the others are wrong
Clobetasol 0.05% scalp solution is a high-potency topical corticosteroid reserved for severe or thick plaque scalp disease in short courses, and risks atrophy and telangiectasia with chronic use.
Hydrocortisone 1% topical lotion is a low-potency corticosteroid that may calm facial erythema but does not address the underlying Malassezia overgrowth and is not the guideline first-line for scalp disease.
Calcipotriene 0.005% solution is a vitamin D analogue useful when there is sebopsoriasis overlap, not the first-line choice for routine seborrheic dermatitis.
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Chronic relapsing pruritic inflammatory dermatosis driven by skin barrier dysfunction and Th2 immune skewing; part of the atopic march.
Chronic relapsing dermatitis of sebum-rich areas associated with Malassezia overgrowth; manifests as cradle cap (infants) and dandruff (adults).
Classic presentation
Flexural 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,…
Greasy yellow scale on erythematous base in sebaceous distribution; nasolabial fold involvement; postauricular fissures.; Mild pruritus or burning, especially scalp; Visible scaling and erythema, often worse in winter; Cosmetic concern, embarrassment; Scalp: fine flaky to thick greasy yellow scale; diffuse or patchy; erythema; Face:…
Workup / key labs
Hanifin 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…
Clinical: scaling and erythema in characteristic sebaceous distribution with chronic relapsing course.; Clinical diagnosis; Consider HIV testing if sudden, severe, or refractory disease, especially in young adults; KOH preparation if tinea or pityriasis versicolor cannot be excluded; Skin biopsy rarely needed; shows spongiosis with…
Imaging
Not indicated
Not indicated
First-line treatment
Skin 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,…
Adult scalp (dandruff/mild-moderate): ketoconazole 2% shampoo, selenium sulfide 2.5% shampoo, zinc pyrithione 1-2% shampoo, ciclopirox 1% shampoo, or coal tar shampoo — 2-3x/week, lather and leave on 5 min before rinsing; Adult scalp (severe/plaque): high-potency topical corticosteroid solution/foam — clobetasol 0.05%, fluocinonide —…
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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.