Psammotherapy in Porto Santo island (Madeira archipelago)

Abstract

Psammotherapy is a practice that uses sand-baths for therapeutic purposes. Sand-baths in the biogenic carbonate sand from Porto Santo Island, in the archipelago of Madeira, constitutes a good example of the positive interaction of minerals on human health. Recent studies provided much information on relevant physical and chemical properties that could explain this sand’s 200-year-long use, although on a much empirical manner, for the treatment of muscular-skeletal (rheumatic and orthopedic) diseases, such as rheumatoid arthritis, gout, osteoporosis, and fibromyalgia. The biogenic carbonate sand from Porto Santo Island consists mainly of bioclasts of calcareous red algae (Rhodophyta), sand-bathing traditionally taking place in the dry sand of the transition zone beach/frontal dune, along the southern coast of the island. Analysis of chemical data shows that Ca, Mg and Sr are the major elements of the biogenic carbonate sand from Porto Santo, elements which are bio-essential for human health. P, S, Si, Al, I, Br, F, B, V, Zn, Cu, Fe, and Se were the minor/trace elements identified in the same sand. The average grain size of this biogenic carbonate sand is estimated at 0.200mm, all sand grain sizes ranging between 0.063mm and 0.500mm. Also, the shape of sand grains is mainly tabular or platy, an essential characteristic for a good adhesion to human skin. In order to be therapeutically effective, sand-bathing in the biogenic carbonate sand from Porto Santo requires sand temperature to be slightly higher (40-42ºC) than body temperature (37ºC), so as to promote body sweating, an essential condition for the interaction sand/human body. The dermal absorption of the bio-essential elements liberated from sand dissolution is responsible for the healing properties of sand-bathing.