Emollients soften skin and moisturisers add moisture. They are used to correct dryness and scaling of the skin and are an effective treatment for mild irritant contact dermatitis.
Dry skin results from lack of water in the stratum corneum. Water loss from the skin is increased by low humidity, wind, increasing age, diuretics, hypothyroidism and loss of sebum. Sebum is removed by washing with hot water and soap, detergents and solvents. Scaly skin arises from partial detachment of groups of corneocytes from the skin surface and is especially prominent in eczema, psoriasis and ichthyosis.
To correct dry skin, reduce bathing, use a non-soap cleanser and apply a moisturiser or emollient.
Occlusive emollients consist of oils of non-human origin (wool-fat, mineral oil etc), either in pure form or mixed with varying amounts of water through the action of an emulsifier to form a lotion or cream. A large variety are available, reflecting that there is no 'right' moisturiser for all patients; the most suitable one often having to be found by trial and error.
The choice of occlusive emollient depends upon the area of the body and the degree of dryness and scaling of the skin. Lotions are used for the scalp and other hairy areas and for mild dryness on the face, trunk and limbs. Creams are suitable for moderate dry skin. Ointments are recommended for very dry scaly areas, but many patients find them too greasy. Aqueous cream is a good all-round moderate-strength moisturiser that suits many patients because it is non-greasy, cheap and available in bulk with or without prescription. Because it contains an emulsifier, aqueous cream can mix with sweat and it can be washed off. Aqueous cream can be made greasier to suit individual preferences by adding white soft paraffin. Typically, 250g (or ml) to 1Kg (1l) are needed and liberal and regular usage is to be encouraged.
Humectant / keratolytics are particularly important in management of the ichthyoses (inherited or acquired scaly disorders of the skin) but urea and lactic acid preparations often sting if applied to broken (scratched or cracked) skin.
Adverse reactions to emollients include:
Topical steroids have revolutionized the treatment of inflammatory skin disease since they were introduced in the late 1950s. Topical steroids are conventionally classified according to their strength. As a general rule, use the weakest possible steroid that will do the job.
Table 1: Topical steroids available in New Zealand
Class 1: very potent (up to 600 times as potent as hydrocortisone)
Class 2: potent (I50-100 times as potent as hydrocortisone)
Class 3: moderate (2-25 times as potent as hydrocortisone)
Class 4: mild
Steroids are absorbed at different rates depending on the thickness of the stratum corneum. A steroid that works on the face may not work on the palm. But a potent steroid may cause side effects on the face.
Absorption is greater in an ointment base, in the presence of a keratolytic agent such as salicylic acid and under occlusion.
Percutaneous absorption of topical steroids may rarely result in systemic side effects. More than 50g of clobetasol propionate or 500g of hydrocortisone each week can result in adrenal gland suppression in an adult and/or eventually Cushing's syndrome. Proportionally smaller quantities may affect children.
Local side effects of topical steroids are more common and include:
The risk of these side effects depends on the strength of the steroid, the length of application, the site treated, and the nature of the skin problem. A potent steroid cream applied to the face results in side effects within a few weeks. 1% hydrocortisone cream on hands and feet would be most unlikely to cause problems.
The only available injectable steroid is triamcinolone acetonide as 1ml ampoules of 10mg/ml or 40mg/ml. Blebs of 0.05 to 0.1ml can be cautiously injected into the dermis at 1cm intervals to a maximum of 1 to 2ml, for the following inflammatory skin diseases:
Injections should not be repeated for 4 to 6 weeks. The main complication, atrophy, arises if the injection is delivered into subcutaneous tissue instead of the dermis. Infection, sterile abscesses and hypopigmentation occur rarely.