DERMATITIS AND ECZEMA
Dermatitis implies inflammation of the skin and can be due to many causes. It is usual to prefix the term with the causal agent, e.g. solar dermatitis. The characteristic features of dermatitis are:
A RED AND HOT SKIN. Dermatitis affects the epidermis and superficial dermis.
OEDEMA IN ACUTE STAGES. This separates the keratinocytes (spongiosis) and produces intradermal vesicles.
WEEPING AND OOZING of fluid on to surface. Crusting is seen in acute phases and scaling and fissuring in chronic stages.
EXCORIATION produced by intense itching. Chronic scratching leads to secondary thickening or lichenification of skin.
IMPAIRED THERMOREGULATION and an increased blood flow leading to cardiac failure in very severe cases.
Acute and chronic stages can be seen in the same individual and the acute can resolve completely, leaving no skin abnormalities.
The meaning of the word ‘eczema’ is ‘flowing over’, which describes some of the above inflammatory changes. The words eczema and dermatitis are used somewhat interchangeably because in both conditions similar inflammatory changes occur in the skin. Use of the term ‘eczema’ avoids the word ‘dermatitis’, which often conjures up ideas in the patient’s mind of external irritants that may cause contact dermatitis. Eczema occurs following a variety of stimuli.
The original skin disease should be in a quiescent phase before patch testing is done. Systemic steroid therapy may alter the cutaneous response to an allergen.
The back is a convenient site for testing Sites for application of the antigen are clearly labelled and a map of their whereabouts is madeMaterials are diluted in order to prevent irritant reacti ons and suspended in white soft paraffin White soft paraffin should be used alone in some sites as a control
Each substance is then placed within an aluminium disc and kept in place next to the skin by adhesive strapping
The patches are taken off and an initial reading is made after 48 hours
A positive reaction is indicated by an area of eczema Further readings are taken at 96 hours Blistering may indicate a non-specific irritant effect but it can occur with soap or detergent materials
Endogenous eczema (atopic dermatitis)
The word ‘atopy’ implies a capacity to hyper-react to common environmental factors. It can be demonstrated by multiple positive skin-prick tests (see p. 651). A positive test to a specific antigen does not necessarily indicate that this antigen is involved in causation of the skin disease, and removal of the antigen, e.g. from the diet, often does not improve the skin condition. The skin lesion may be caused by CD4 T cells infiltrating the skin and producing the cytokines interferon yand interleukins 2 and 4. Serum levels of the IgE antibody are elevated in atopic eczema as in all atopic diseases; higher values are seen when eczema is combined with asthma. The significance of these raised levels in the pathogenesis of the eczema is unclear.
Diet A few patients may be able to correlate the onset of itching and exacerbation of eczema with dietary factors such as eggs and milk and the removal of the food item will often improve the skin condition. Dietary changes need to be assessed over a prolonged period.
There is a hereditary predisposition; when both parents have the disease, the risk of their offspring developing eczema is approximately 60%. Exacerbating factors Non-specific stimuli such as heat, humidity, drying of the skin and contact with woollen clothing may cause a flareup
of disease, and patients should be advised to avoid these trigger factors. Irritation may occur following contact urticaria when, for example, foods or animal saliva touch the skin of a sensitized individual. In atopic patients Staphylococcus aureus is found more frequently on the normal skin or nasal mucosa than expected. It is present on 90% of acute eczematous lesions and exacerbates the condition. Herpes simplex may become disseminated on atopic skin (eczemaerpeticum). Aeroallergens, e.g. house-dust mite, are thought to play an active role in facial eczema.
PATTERNS OF DISEASE
Erythema, weeping or scaling usually appear first on the face when the infant is a few months old. Other body sites are less commonly affected. Irritation produces restlessness and the child may rub its face or scalp on a pillow or the cot-side. With time there is a gradual spread of the dermatitis to the flexures. Flexural or childhood eczema In toddlers and older children the skin folds are typically involved. Facial involvement may persist, partly owing to climatic factors, e.g. sunlight and low humidity.
In those whose disease continues into adult life, the flexures at the neck, elbow, wrist, ankle or knee and the limbs are often involved. Chronic eczematous changes are common on the face, although any site on the body may be involved.
With a typical pattern of involvement and an early onset, the prognosis is good. Some children will lose their disease in infancy, whilst others improve gradually so that by the early teens more than 90% will be clear of disease. Localized recurrence may occur in adult life if the skin is unduly stressed, e.g. the hands of nurses or hairdressers. An unusual pattern of eczema over extensor surfaces (reversed pattern) coming on later in childhood may represent more recalcitrant disease and the prognosis should be guarded.
About one-third of atopic children have a dry skin in addition to eczema. Keratosis pilaris or ichthyosis vulgaris are associated conditions. The regular use of emollients such as aqueous cream or emulsifying ointment applied to a damp skin after bathing or used instead of soap is fundamental to a treatment regimen. The use of per fumed soaps and ‘b bble baths’ should be avoided. Nonperfumed cleansers and gels should be used for washing, with the use of soap limited. Sunny seaside holidays or UV light treatment will often stabilize the skin condition. For widespread regular use over months or years, a mild topical corticosteroid (Table 20.1), e.g. 1% hydrocortisone, is suitable; the cream base is the form best tolerated- the occlusive nature of ointments may, with sweating, promote itching. Localized disease may requireshort courses of more potent topical corricosteroids on some occasions, especially when the skin is markedly thickened. The addition of tar as an alcoholic solution or as crude coal tar may also improve lichenified skin. Bacterial infection seen with gross excoriation or with fissuring of the skin is treated with a steroid-antibiotic combination and systemic antibiotics may be required. The treatment of associated atopic disease, e.g. asthma, may in turn improve the state of the skin, the child’s ellbeing
and sleep pattern. Sedative antihistamines, such as promethazine hydrochloride elixir at night, will also help to prevent restless sleep and ceaseless scratching. The reduction of house-dust mite exposure (see p. 654) may improve facial eczema.