Atopic Dermatitis (Eczema)
Chronic relapsing pruritic inflammatory dermatosis driven by skin barrier dysfunction and Th2 immune skewing; part of the atopic march.
Also known as: atopic dermatitis, eczema, AD, atopic eczema, infantile eczema
Overview
A chronic, intensely pruritic, relapsing inflammatory skin disease characterized by age-dependent distribution of eczematous patches, often associated with personal or family history of atopy (asthma, allergic rhinitis, food allergy).
Epidemiology
Affects 15-20% of children and 7-10% of adults in the US. Onset before age 5 in 85% of cases. Higher prevalence in urban populations and developed countries. Persists into adulthood in ~50% of pediatric cases.
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Risk factors
- Family or personal history of atopy (asthma, allergic rhinitis, food allergy)
- Filaggrin (FLG) loss-of-function mutations — strongest genetic risk factor
- Low humidity climates, harsh soaps, frequent bathing without moisturizer
- Aeroallergens, food allergens (in young children), Staphylococcus aureus colonization
- Stress, sleep disturbance, sweating
Pathophysiology
Combination of (1) epidermal barrier dysfunction — filaggrin and lipid deficiency, increased transepidermal water loss — and (2) Th2-skewed immune response with IL-4, IL-13, IL-31 (pruritus), and IL-22 driving inflammation, epidermal hyperplasia, and impaired antimicrobial defense. Itch-scratch cycle perpetuates barrier disruption.
Clinical presentation
Symptoms
- Intense pruritus — required feature; often worse at night, disrupts sleep
- Chronic relapsing course with flares and remissions
- Dry skin (xerosis) between flares
Signs / physical exam
- Infants (0-2 yrs): erythematous, weeping, crusted patches on cheeks, scalp, extensor extremities; spares diaper area
- Children (2-12 yrs): lichenified plaques in flexural areas — antecubital, popliteal fossae, neck, wrists, ankles
- Adults: chronic lichenification of hands, neck, eyelids, flexures; nipple eczema; head-and-neck dermatitis (Malassezia)
- Associated features: Dennie-Morgan infraorbital folds, allergic shiners, keratosis pilaris, ichthyosis vulgaris, palmar hyperlinearity, white dermatographism
Classic findings
Flexural eczematous patches with lichenification in a child or adolescent with personal/family atopy.
Differential diagnosis
- Seborrheic dermatitis — Greasy yellow scale on scalp, eyebrows, nasolabial folds; less pruritic; infant cradle cap can mimic infantile AD
- Allergic / irritant contact dermatitis — Sharply demarcated lesions matching exposure pattern; patch testing positive for contactant
- Psoriasis — Well-demarcated thick silvery plaques on extensor surfaces, scalp, nails; Auspitz sign
- Scabies — Intense nocturnal pruritus, burrows in web spaces/wrists, household contacts affected
- Cutaneous T-cell lymphoma (mycosis fungoides) — Adult-onset 'eczema' refractory to therapy in non-sun-exposed areas; skin biopsy
- Tinea corporis — Annular plaques with raised scaly border and central clearing; KOH positive
- Nummular dermatitis — Coin-shaped well-circumscribed plaques on extremities; can overlap with AD
Diagnostic workup
Diagnostic criteria
Hanifin and Rajka criteria (3 major + 3 minor) or AAD simplified criteria. Essential features: pruritus + eczematous dermatitis in age-typical distribution + chronic/relapsing course.
Labs
- Clinical diagnosis — no required labs
- Serum total IgE often elevated; allergen-specific IgE or skin-prick testing only if clear allergic trigger suspected
- Skin culture if secondary infection suspected
- Skin biopsy reserved for atypical or refractory cases to exclude CTCL
Imaging
- Not indicated
Diagnostic algorithm
| Age Group | Typical Distribution | Lesion Features |
|---|---|---|
| Infant (0-2) | Cheeks, scalp, extensor extremities; spares diaper area | Acute erythematous weeping crusted patches |
| Childhood (2-12) | Flexural — antecubital, popliteal, neck, wrists, ankles | Subacute scaly excoriated plaques, early lichenification |
| Adolescent / Adult | Flexures, hands, eyelids, neck, nipples | Chronic lichenified plaques, post-inflammatory pigment change |
Treatment
First-line
- 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, infants), triamcinolone 0.1% (mid; trunk/extremities), clobetasol 0.05% (high; lichenified plaques, palms/soles)
- Topical calcineurin inhibitors — tacrolimus 0.03-0.1% ointment, pimecrolimus 1% cream — steroid-sparing, especially face/eyelids/folds
- Topical PDE4 inhibitor — crisaborole 2% ointment (≥3 months old)
- Topical JAK inhibitor — ruxolitinib 1.5% cream (mild-moderate AD, ages ≥12)
- Trigger avoidance: harsh soaps, fragranced products, wool, sweating; address food allergies if proven
Moderate-severe / refractory
- Wet-wrap therapy with mid-potency topical steroid for acute flares
- Phototherapy: narrowband UVB (preferred), UVA1
- Biologics — dupilumab (anti-IL-4Rα; ages ≥6 months), tralokinumab and lebrikizumab (anti-IL-13; ages ≥12)
- Oral JAK inhibitors — upadacitinib, abrocitinib (ages ≥12); boxed warnings for thrombosis, malignancy, MACE
- Conventional systemics — cyclosporine, methotrexate, azathioprine, mycophenolate (off-label, narrow use)
Secondary infection
- Staph impetiginization: cephalexin or dicloxacillin × 7-10 days; mupirocin if localized; bleach baths (0.005%) twice weekly for chronic colonization
- Eczema herpeticum (HSV superinfection): rapid-onset monomorphic punched-out vesicles, fever — IV or oral acyclovir, ophthalmology if periocular
Second-line / adjunct
- Sedating antihistamine (hydroxyzine, diphenhydramine) at night for sleep — does not treat itch directly
- Non-sedating antihistamines have minimal benefit in AD
- Address psychosocial impact — sleep, school/work, mental health
Complications
- Bacterial superinfection (S. aureus) and impetiginization
- Eczema herpeticum — disseminated HSV; dermatologic emergency
- Atopic march: progression to allergic rhinitis and asthma
- Sleep disturbance, ADHD-like inattention, depression, anxiety
- Ocular: keratoconus, atopic keratoconjunctivitis, cataracts (long-term steroid use)
- Growth impairment in severe pediatric disease
- Skin atrophy and striae from prolonged potent topical steroids
PANCE pearls
- Pruritus is required for diagnosis — 'eczema' without itch is not atopic dermatitis.
- Use the fingertip unit (FTU) rule: 1 FTU = ~0.5 g, covers area of 2 adult palms.
- Topical calcineurin inhibitors carry a boxed warning for theoretical malignancy risk, but long-term data have not substantiated this — they remain safe and effective for face/folds.
- Bleach baths (1/4 to 1/2 cup household bleach in full tub) twice weekly reduce S. aureus burden and flare frequency.
- Sudden monomorphic punched-out erosions and fever in a child with AD = eczema herpeticum until proven otherwise — start acyclovir immediately.
References
- AAD 2024 — Guidelines of Care for the Management of Atopic Dermatitis in Adults with Topical Therapies (Davis et al., J Am Acad Dermatol 2024)
- AAP 2014 — Atopic Dermatitis: Skin-Directed Management — American Academy of Pediatrics (Tollefson, Bruckner, Pediatrics 2014)
- Hanifin-Rajka — Diagnostic Features of Atopic Dermatitis (Hanifin and Rajka, Acta Derm Venereol Suppl 1980)
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