Chronic Rash (Adult/Child)

Introduction: Chronic rashes are defined as skin eruptions persisting for ≥6 weeks. In children, they are most often due to atopic dermatitis, psoriasis, or infections. In adults, chronic rashes may indicate autoimmune disease, contact reactions, or chronic infections. A careful history, thorough examination, and selective investigations are essential to avoid misdiagnosis.

📋 Detailed History

• Duration: How long has the rash been present?
• Onset: Gradual or sudden? Childhood onset suggests atopic dermatitis.
• Pattern: Intermittent flare-ups (eczema/urticaria) vs persistent plaques (psoriasis).
• Triggers: Allergens 🐈, foods 🍫, soaps 🧼, temperature 🌡️, or stress 😰?
• Family History: Atopy (eczema, asthma, hay fever) or autoimmune disease.
• Symptoms: Itchiness (eczema, scabies), scaling (psoriasis, fungal), pain, discharge, fever, systemic illness.

🔍 Physical Examination

• Distribution: Flexural (eczema), extensor (psoriasis), scalp (tinea capitis), web spaces (scabies).
• Morphology: Papules, vesicles, plaques, scales, crusts.
• Chronic signs: Lichenification (eczema), nail pitting (psoriasis), hypopigmentation (post-inflammatory).
• Systemic clues: Fever, lymphadenopathy, weight loss (consider systemic disease or infection).

🧾 Differential Diagnosis

• 👶 Children: Atopic dermatitis, tinea capitis, impetigo, scabies, genetic syndromes (e.g., ichthyosis).
• 🧑 Adults: Psoriasis, contact dermatitis, chronic urticaria, cutaneous T-cell lymphoma, fungal infections.
• All ages: Atopic dermatitis, psoriasis, tinea, bacterial infection, scabies.

🧪 Investigations (when indicated)

• 🧫 Skin swab: Culture for bacteria/viruses.
• 🔬 Skin scraping + KOH prep: Fungal infections (tinea, candida).
• 📌 Patch testing: Allergens in contact dermatitis.
• 🧪 Biopsy: For atypical, persistent, or suspected autoimmune/lymphoproliferative rashes.
• 🧬 Bloods: IgE (atopy), ANA (lupus), thyroid antibodies (autoimmune rash).

💊 Management Principles

• 🧴 Skin barrier repair: Daily emollients are cornerstone therapy.
• 🚫 Avoid triggers: Allergens, harsh soaps, overheating, scratching.
• 💊 Anti-inflammatory: Topical steroids (hydrocortisone → clobetasol) depending on severity/site.
• 🌙 Antihistamines: Sedating at night for itch relief.
• 📈 Step-up therapy: Topical calcineurin inhibitors, phototherapy, or systemic agents if severe.

🔑 Condition-Specific Strategies

• Atopic Dermatitis (Eczema): Emollients, mild-to-moderate steroids, tacrolimus/pimecrolimus for sensitive sites, education on flare prevention.
• Psoriasis: Vitamin D analogues + topical steroids, coal tar, phototherapy, systemic therapy (methotrexate, ciclosporin, biologics).
• Contact Dermatitis: Allergen/irritant avoidance, patch testing, topical steroids.
• Fungal Infections (Tinea): Topical antifungals (clotrimazole, terbinafine), oral antifungals for scalp/nails.
• Impetigo: Topical/oral antibiotics (flucloxacillin, fusidic acid).
• Scabies: Permethrin cream to whole body, treat contacts, oral ivermectin if resistant.

📌 Referral

• Dermatology: Unclear or refractory rashes, severe psoriasis, suspected cutaneous lymphoma.
• Infectious diseases: Refractory fungal or parasitic infections.
• Paediatrics: Genetic or metabolic skin disorders in children.

👨‍👩‍👧 Parent / Patient Education

• Daily emollient use, short lukewarm baths, avoid soap.
• Long-term nature of conditions like eczema and psoriasis – set realistic expectations.
• Prevent secondary infection: trim nails, discourage scratching.
• Importance of adherence: many failures are due to underuse of topical therapy.

🧾 Clinical Cases

Case 1 – Atopic Dermatitis in a Child

A 6-year-old girl has itchy red patches in the flexures of elbows and knees since infancy. Mother has asthma and father has hay fever. Scratching at night is severe.

🔑 Teaching point: Classic flexural distribution, personal/family atopy, and itch = eczema.

Case 2 – Chronic Plaques in an Adult

A 40-year-old man presents with thick, well-demarcated, scaly plaques on extensor elbows and knees. He has nail pitting and reports his father had similar lesions.

🔑 Teaching point: Psoriasis – autoimmune, chronic, often with family history and nail involvement.

Case 3 – Persistent Scalp Rash

A 10-year-old boy with patchy hair loss and scaly lesions on the scalp. Microscopy of scrapings reveals fungal hyphae.

🔑 Teaching point: Tinea capitis – needs systemic antifungal (e.g., griseofulvin) not just topical cream.

Case 4 – Itchy Rash in Adult with New Job

A 28-year-old nurse develops an itchy rash on the hands after frequent hand washing at work. Patch testing shows nickel sensitivity.

🔑 Teaching point: Contact dermatitis – occupational, managed by allergen avoidance and topical steroids.