Dermatology, Venereology and Leprosy
Dermatitis and Eczema
Eczema for MBBS and NEET-PG: atopic, allergic and irritant contact dermatitis, patch testing, erythroderma, fixed drug eruption and Stevens-Johnson syndrome, mapped to NMC codes DR12.
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Dermatitis and Eczema
Eczema for MBBS and NEET-PG: atopic, allergic and irritant contact dermatitis, patch testing, erythroderma, fixed drug eruption and Stevens-Johnson syndrome, mapped to NMC codes DR12.
Eczema is the commonest inflammatory skin disease and covers atopic, contact and other patterns. This chapter covers the atopic barrier defect and its distribution, allergic and irritant contact dermatitis with patch testing, lichenification, the emergency of erythroderma, the drug eruptions including Stevens-Johnson syndrome, and the emollient-based treatment ladder.
High-yield: Dermatitis and Eczema
- Eczema and dermatitis are interchangeable terms for an inflammatory skin reaction with itching, redness, vesicles when acute and lichenification when chronic.
- Atopic dermatitis is a chronic itchy condition of childhood linked to a personal or family history of asthma and allergic rhinitis, the atopic triad.
- In infants atopic eczema affects the face and extensor surfaces, while in older children it settles in the flexures such as the antecubital and popliteal fossae.
- A defective skin barrier, in part from filaggrin gene mutations, underlies the dryness and susceptibility of atopic skin.
- Allergic contact dermatitis is a type IV delayed hypersensitivity reaction and is confirmed by patch testing to identify the allergen.
- Irritant contact dermatitis results from direct chemical damage and, unlike the allergic type, can occur on first exposure without sensitisation.
- Nickel, chromate, fragrances and rubber chemicals are common contact allergens, and hand eczema is often occupational.
- Chronic scratching leads to lichenification, a thickening of the skin with exaggerated markings.
- Erythroderma is a generalised inflammatory redness involving more than 90% of the skin surface, with risks of fluid loss, hypothermia and high-output cardiac failure.
- Common causes of erythroderma are pre-existing eczema or psoriasis, drug reactions and cutaneous lymphoma.
- Fixed drug eruption produces one or more well-defined round dusky patches that recur at exactly the same site each time the drug is taken.
- Stevens-Johnson syndrome and toxic epidermal necrolysis are severe drug reactions with mucosal erosions and skin detachment, separated by the body surface area involved.
- Emollients and the avoidance of triggers are the foundation of eczema care, with topical corticosteroids for flares.
- Topical calcineurin inhibitors, wet wraps, antihistamines for itch and treatment of secondary infection are used as required in eczema.
Types of eczema and severe reactions
- **Atopic:** Itchy flexural eczema, atopic triad, barrier defect. Emollients and topical steroids.
- **Allergic contact:** Type IV hypersensitivity to nickel, chromate and others. Patch testing.
- **Irritant contact:** Direct chemical damage, may occur on first exposure, often occupational.
- **Severe reactions:** Erythroderma (over 90% surface); fixed drug eruption; SJS and TEN.
NMC competencies in this chapter
- **DR12.1:** Aetiopathogenesis of eczema
- **DR12.2:** Identifying eczema and differentiating it from lichenification
- **DR12.3:** Classifying and grading eczema
- **DR12.4:** Indications and pharmacology of drugs used to treat eczema
- **DR12.5:** Definition, causes and identification of erythroderma
- **DR12.6:** Distinguishing exfoliative dermatitis from other skin lesions
- **DR12.7:** Distinguishing fixed drug eruption and Stevens-Johnson syndrome
Frequently Asked Questions
What is the difference between allergic and irritant contact dermatitis?
Allergic contact dermatitis is a type IV delayed hypersensitivity reaction that needs prior sensitisation and is confirmed by patch testing, while irritant contact dermatitis is direct chemical damage that can occur on first exposure.
Where does atopic eczema appear at different ages?
In infants it affects the face and extensor surfaces, and in older children and adults it settles in the flexures such as the antecubital and popliteal fossae. It is linked to the atopic triad of asthma, hay fever and eczema.
Why is erythroderma an emergency?
When more than 90% of the skin is inflamed, the patient can lose heat and fluid, become hypothermic and develop high-output cardiac failure, so it needs urgent supportive care and treatment of the cause.
What is a fixed drug eruption?
A well-defined round dusky patch that recurs at exactly the same site each time the responsible drug is taken, leaving pigmentation between episodes.
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