In exogenous irritant or allergic contact dermatitis the mainstay of treatment is to identify the precipitating agent and to avoid it if at all possible. Otherwise the same general principles apply to the treatment of all forms of eczema. If there is a possibility that the eczema may be infected, skin swabs should be submitted for bacterial culture and sensitivity and, if appropriate, an antibiotic such as flucloxacillin should be prescribed. For acute, particularly wet and weeping eczema, astringent solutions such as potassium permanganate (1:10,000) are indicated. The involved area, such as hands or feet, can be placed in a bowl of the solution or, alternatively, wet gauze swabs may be applied directly to the skin. The majority of patients with eczema have a chronic, dry scaling, rash. These patients should be advised to use emollients frequently. They should also avoid soap and use soap substitutes, such as emulsifying ointment or Diprobase, wherever possible. Emollient bath oil and gels should be used when bathing, and ointments and creams applied to the skin after bathing. If these simple measures fail to settle the eczema, a topical corticosteroid may be necessary. Topical corticosteroids have an anti-inflammatory, immunosuppressive, antimitotic, and vasoconstrictive action on the skin. These actions are mediated by a nuclear receptor for hydrocortisone to which other steroids also bind (9). The stronger the affinity of the steroid for the receptor the more potent the steroid. The anti-inflammatory action of the corticosteroids depends on the induction of peptides, known as lipocortins, which antagonize the actions of phospholipase-A2 which acts to release arachidonic acid from membrance phospholipids. Other effects of corti-costeroids include lysosomal and cellular membrane stabilization, a reduction in the number of epidermal Langerhans cells, and modulation of the migration of inflammatory cells.
Topical corticosteroids are classified as being mild (e.g., hydrocortisone 1%), moderately potent (e.g., clobetasone butyrate 0.05%), potent (e.g., betamethasone valerate 0.1% or hydrocortisone butyrate 0.1%), or as very potent (e.g., clobetasol propionate 0.05%).
Creams are suitable for moist or weeping areas of eczema, whereas ointments should be used for dry, scaly, or lichenified areas. Local side effects of topical steroids include masking or worsening of infection (especially fungal infections), thinning of the skin, induction of striae, bruising and telangectasia, on aggravation of rosacea.
Use of more potent topical steroids may result in pituitary-adrenal axis suppression, iatrogenic Cushing's syndrome, and stunted growth.
In general, one should aim to use a steroid of sufficient potency to control the eczema, and then aim to reduce the potency of the topical steroid preparation as the eczematous rash improves. There is a tendency for the eczematous rash to rebound when treatment is stopped or the potency of the topical steroid is decreased. The aim should be for the patient to use the least potent topical corticosteroid that will control the rash and, preferably, to use simple emollients only. It is important that patients are prescribed adequate quantities of topical therapy and that these are applied regularly. There is doubt as to whether topical steroids need to be applied twice daily and some topical steroids such as fluticasone propionate 0.05% (Cutivate) or mometasone furoate 0.1% (Elocon) are claimed to be effective when applied once daily. Patients may apply moisturizers ad lib in between applications of cortico-steroids.
Coal tar preparations may be helpful with reducing the pruritis of eczema and may be particularly valuable in lichenified and localized eczema, such as lichen simplex. Occlusive bandaging, such as Viscopaste, Coltapaste, or Ichthopaste bandages, may be of benefit, particularly if the eczema is excoriated. The bandages are soothing and prevent further excoriation. Some patients, however, may develop sensitivity to the preservatives found in these bandages.
Infection with S. aureus can frequently exacerbate eczema and patients may benefit from the use of a combined topical steroid antibiotic preparation such as Fucibet. However, topical antibiotics may cause sensitization, and, in recent years, the problem of sensitization to topically applied corticosteroids themselves has also been recognized, and should be considered if the eczema fails to settle.
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