Eczema
D E FI N I T ION
A pruritic papulovesicular skin reaction to endogenous or exogenous agents.
AE T IOLOGY
Numerous varieties caused by a diversity of triggers.
Exogenous: Irritant, contact, phototoxic.
Endogenous: Atopic, seborrhoeic, pompholyx, varicose, lichen simplex.1
Irritant: Prolonged skin contact with a cell-damaging irritant (e.g. ammonia in nappy rash).
Contact: Type IV delayed hypersensitivity to allergen (e.g. nickel, chromate, perfumes, latex
and plants).
Atopic: Two major models currently exist to explain the pathogenesis:
1 Impaired epidermal barrier function due to intrinsic structural and functional skin abnormalities
(predominant model).
2 Immune function disorder in which Langerhans cells, T cells and immune effector cells
modulate an inflammatory response to environmental factors (traditional model).
Seborrhoeic: Pityrosporum yeast seems to have a central role.
Varicose: Increased venous pressure in lower limbs.
E P IDEMIOLOGY
Contact: Prevalence 4 %.
Atopic: Onset is commonly in the first year of life. Childhood incidence 10–20 %.
H ISTORY
Itching (can be severe), heat, tenderness, redness, weeping, crusting.
Enquire into occupational exposures or irritants used at home (e.g. bleach). Enquire into
family/personal history of atopy (e.g. asthma, hay fever, rhinitis).
EXAMINA T I ON
Acute: Poorly demarcated erythematous oedematous dry scaling patches. Papules, vesicles
with exudation and crusting, excoriation marks.
Chronic: Thickened epidermis, skin lichenification, fissures, change in pigmentation.
By type:
Contact and irritant: Eczema reaction occurs where irritant/allergen comes into contact
with the skin. In some cases, autosensitization (spread to other sites) can occur in contact
eczema.
Atopic: Particularly affects face and flexures.
Seborrhoeic: Yellow greasy scales on erythematous plaques, particularly in the nasolabial
folds, eyebrows, scalp and presternal area.
Pompholyx: Acute and often recurrent painful vesiculobullous eruption on palms and soles.
Varicose: Eczema of lower legs, usually associated with marked varicose veins.
Nummular: Coin shaped, on legs and trunk.
Asteatotic: Dry, ‘crazy paring’ pattern.
INVE S T I G A T IONS
Contact:
Skin patch testing: Disc containing postulated allergen is diluted and applied to back for 48 h.
Positive if allergen induces a red raised lesion.
Atopic: Laboratory testing, including IgE levels, are not used routinely and are not currently
recommended.
Swab for infected lesions (bacteria, fungi and viruses).
1 Lichen simplex is the thickening of skin secondary to a cycle of itch – scratch – itch, and is characterized by
well-demarcated hyperpigmented lichenified plaques.
Eczema (continued)
MANAGEMENT
Irritant or contact: Avoid precipitant. Barrier protection (e.g. gloves, barrier cream).
Atopic: Avoid precipitants. Topical steroids. Low potency steroids are used for face and skin
folds (areas at high risk for atrophy). The use of potent steroids in these areas should be
prescribed by a dermatologist. Tacrolimus (calcineurin inhibitor) ointment for moderate
to severe eczema not responding to potent steroids. Systemic immunosuppressants or
phototherapy may be helpful in very severe cases.
Topical or systemic antibiotics for secondary infection. Medicated bandages (e.g. zinc paste
for severe limb eczema). For pruritus, antihistamines. Emollients (in bath water, as soap
substitute or by direct application to affected area).
Seborrhoeic: Topical 1%hydrocortisone and antifungal. Ketoconazole shampoo for scalp
involvement.
Pompholyx: Potent topical steroids, potassium permanganate salts, systemic steroids in
severe attacks.
COMPL I C A T IONS
Secondary infection, particularly from Staphylococcus aureus and HSV.
HSV superinfection can be life-threatening. " predisposition to Molluscum contagiosum.2
P ROGNOS I S
Good prognosis for irritant eczema if the relevant agent is identified and
avoided. Endogenous eczema may have a chronic relapsing course. Of all patients, 90%with
atopic eczema recover by puberty.
Wiskott–Aldrich syndrome: Association of eczema, thrombocytopaenia, immunological
abnormalities and a predisposition to lymphoma and leukaemia.
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