Nearly all preparations available without prescription for skin conditions are treatments for dry skin, with which most of this article will be concerned. Dry skin is the result of inadequate moisture content in the stratum corneum and is associated with a range of conditions, including contact dermatitis, atopic eczema, psoriasis, and with various systemic disorders such as hypothyroidism, arthritis and autoimmune conditions.

Products containing one of three active moieties are licensed for specific skin conditions: dithranol and coal tar for psoriasis, and the steroidal anti-inflammatories clobetasone and hydrocortisone for eczema and dermatitis.

Formulations

The principle of treatment for dry skin is rehydration of the stratum corneum to its normal level of 10-20 per cent. Moisturising preparations achieve this by replacing water lost from the epidermis, although this is only possible to a limited extent, and by preventing further evaporation.

The latter may be achieved simply by applying a film of oil to the skin while it is wet or directly after it has been wetted and dried, for example, by adding oil to a bath or applying it directly afterwards.