CHEMICAL ANALYSIS AND IN VITRO UV-PROTECTION CHARACTERISTICS OF CLAYS TRADITIONALLY USED FOR SUN PROTECTION IN SOUTH AFRICA
SUMMARY
Clays have been used in southern Africa as photoprotectants by the indigenous people. Typically, two types of clay are used: one white in colour and the other red. In this work, the two clays were identified and characterized, and their in vitro SPF values measured. The clays afford a low SPF but offer broadspectrum protection. No cutaneous side effects from the use of these clays are known. Further consideration should be given to the potential use of clays in sunscreen preparations.
In hot, sunny climates as experienced in Durban, South Africa, photoprotective measures are required all year round to prevent erythema, irrespective of photoskin type (1). Indigenous African women, particularly those from rural areas, use local clay material for photoprotection and decorative purposes. These women follow a subsistence lifestyle and are outdoors for many hours each day, gardening, fetching wood and water, cooking and performing other chores. They also lack the means to purchase commercial sunscreen products. Although these women typically present
with Fitzpatrick skin types 5 and 6, for which skin cancer is less common, photoprotection is important to prevent hyperpigmentation disorders such as melasma.
Clay minerals are widely used in the pharmaceutical industry for a variety of purposes in oral and topical applications, as excipients and in aesthetic medicine (2). They have been used since ancient times (2), so it is not surprising that they form part of the heritage in southern Africa. Recently, the ultraviolet (UV)-protective capacity of clays was reported (3).
Two clays are typically used: one white in appearance and the other red. The white clay is known locally as umcaku (isiZulu/isiXhosa) and the red as ibomvu (isiZulu/ isiXhosa). The women mix the clay (100 g) with water (125 cm3) and glycerine (20 cm3) to produce a paste that is applied to the face. The clays are used individually with some women preferring one over the other. The distinct appearance of patients wearing these clays is shown in Fig. 1. As very little is known of the composition and UV efficacy of these clays, it was of interest to undertake a study thereof.