Eczema

Chronic, relapsing, pruritic inflammatory skin condition resulting from a combination of skin barrier dysfunction (filaggrin gene mutations implicated) and immune dysregulation (predominantly Th2-mediated), often part of the "atopic march" alongside asthma and allergic rhinitis. Most commonly begins in infancy/childhood, though adult-onset occurs.

Classified by:

• Distribution/age pattern: infantile (face, scalp, extensor surfaces), childhood (flexural, antecubital/popliteal fossae, wrists, ankles), adult (flexural + hands, face, neck, often more lichenified/chronic)

• Severity: mild, moderate, severe (based on body surface area, intensity of signs, impact on sleep/quality of life, tools: SCORAD, EASI)

• Variants: discoid (nummular) eczema, seborrheic dermatitis (distinct entity, different pattern), hand eczema, asteatotic eczema

• Core features: pruritus (often severe, worse at night), dry skin (xerosis), erythematous ill-defined patches/plaques

• Acute lesions: erythema, papules, vesicles, oozing/weeping, excoriation

• Chronic lesions: lichenification (thickened, accentuated skin markings from chronic scratching), hyperpigmentation/hypopigmentation, fissuring

• Distribution varies by age: flexural surfaces classically involved beyond infancy

• Associated atopic features: personal/family history of asthma, allergic rhinitis, food allergy; keratosis pilaris, ichthyosis vulgaris, Dennie-Morgan infraorbital folds, hyperlinear palms

• Complications:

• Secondary bacterial infection: Staphylococcus aureus: colonization near-universal, overt infection shows weeping, crusting (golden/honey-colored), pustules, worsening despite treatment

• Eczema herpeticum (HSV superinfection: DERMATOLOGICAL EMERGENCY): monomorphic punched-out vesicles/erosions, rapid spread, systemic symptoms (fever, malaise), requires urgent antiviral treatment

• Psychological impact: sleep disturbance, impaired quality of life, anxiety/depression (significant, often underappreciated)

Clinical diagnosis based on history and examination. UK Working Party diagnostic criteria: itchy skin condition PLUS ≥3 of: history of flexural involvement, personal history of asthma/hay fever (or atopic disease in first-degree relative if <4 years), history of generally dry skin in past year, onset <2 years of age, visible flexural dermatitis (or cheeks/forehead/extensor in <4 years).

Investigations not routinely needed; consider if:

• Recurrent/severe infections or atypical presentation: skin swabs for bacterial culture/sensitivity

• Suspected eczema herpeticum: viral PCR/swab, urgent same-day dermatology/ophthalmology if periocular involvement

• Suspected food allergy trigger (esp. infants with moderate-severe eczema): allergy-focused history, specific IgE/skin prick testing (do not routinely test broad panels without clinical correlation)

• Patch testing: if allergic contact dermatitis suspected as co-existing/aggravating factor, particularly in adult-onset or treatment-resistant hand/facial eczema

Differentials: seborrheic dermatitis (greasy scale, different distribution, scalp, nasolabial folds, no significant pruritus), contact dermatitis (irritant or allergic, distribution corresponds to exposure), psoriasis (well-demarcated, silvery scale, extensor surfaces), scabies (burrows, web spaces, contacts affected), tinea corporis (annular, central clearing), fungal infection.

Foundation (all severities):

• Emollients: mainstay, used liberally and frequently (minimum 2–3x/day, even when skin clear), ointments preferred over creams/lotions for dry skin (higher lipid content, less preservative irritation); apply in direction of hair growth to reduce folliculitis

• Avoid known triggers/irritants: harsh soaps, wool fabrics, excessive bathing/hot water, known allergens

• Bathing: lukewarm water, emollient wash products instead of soap, pat dry (don't rub), apply emollient within minutes of bathing ("soak and seal")

Topical anti-inflammatory therapy (flares):

• Topical corticosteroids: potency matched to severity/site:

• Mild (face, flexures, infants): hydrocortisone 1%

• Moderate (limbs, trunk): betamethasone valerate 0.025-0.1%, or clobetasone butyrate 0.05%

• Potent (thick lichenified plaques, palms/soles, resistant): betamethasone dipropionate 0.05%, mometasone furoate 0.1%

• Apply od-bd during flares, fingertip unit dosing guide, step down as improves; caution on face/flexures/prolonged use (skin atrophy, striae, telangiectasia)

• Topical calcineurin inhibitors (steroid-sparing, especially face/flexures/long-term maintenance): tacrolimus ointment 0.03% (children)/0.1% (adults), pimecrolimus cream 1%, burning sensation on application common initially

• "Proactive therapy": twice-weekly application of topical steroid/calcineurin inhibitor to previously affected areas even when clear, reduces flare frequency

Moderate-severe/treatment-resistant disease:

• Wet wrap therapy (bandaging over emollient/topical steroid) for severe flares

• Phototherapy (narrowband UVB): specialist setting

• Systemic therapy (dermatology-initiated):

• Conventional: ciclosporin (rapid but renal/BP monitoring needed), methotrexate, azathioprine (check TPMT before starting), mycophenolate mofetil

• Biologics: dupilumab (anti-IL4/13), first-line biologic, subcutaneous injection; tralokinumab (anti-IL13)

• JAK inhibitors: upadacitinib, abrocitinib, oral, rapid onset, requires monitoring (infection, VTE, lipid, malignancy risk per boxed warnings)

Infection management:

• Secondary bacterial infection: flucloxacillin PO (or topical fusidic acid for very localized), consider decolonization (dilute bleach baths, nasal mupirocin) for recurrent infections

• Eczema herpeticum: urgent oral/IV aciclovir (IV if systemic symptoms, periocular involvement, or infants), same-day dermatology/ophthalmology referral if eye involvement, do not delay for confirmation

Patient education: chronic relapsing-remitting course, adherence to emollient regimen even when clear, trigger avoidance, realistic expectations (control not cure), address itch-scratch cycle (keep nails short, consider antihistamine for sleep disruption though evidence for itch relief itself is limited, sedating antihistamines like hydroxyzine may help via sedation at night).

Referral: dermatology for diagnostic uncertainty, treatment-resistant/severe disease, recurrent infections, suspected eczema herpeticum (urgent), significant psychosocial impact, or consideration of systemic therapy.