Porto Santo's therapeutic sand: what psammotherapy is, and what it is not

Why this sand is different

Almost every beach in mainland Portugal and Europe has siliceous sand, meaning quartz eroded from continental rock. Porto Santo's sand does not come from broken rock, it comes from marine life: bioclasts of calcareous algae, mollusc shells, bryozoans and the fossilised remains of microscopic organisms, accumulated over millennia on the submarine platform surrounding the island. A geological curiosity that surprises almost every visitor: Porto Santo is volcanic in origin, but its sand is golden rather than dark, precisely because it is not ground volcanic rock, it is carbonate of biological origin.

Everything else follows from that composition: the sand contains calcium, magnesium and strontium, the last of these with anti-inflammatory properties, as well as sulphur. And it is that chemical combination, together with heat, that gives the therapeutic practice its substance.

How a session actually works

Psammotherapy is not lying on the beach in the sun. In a controlled clinical setting, the process runs like this:

1. The patient is placed in a sand bath or bed and progressively covered.
2. The sand is heated gradually, to a range of roughly 40 to 43°C.
3. As sweating begins, perspiration partially dissolves the carbonates in the sand, allowing calcium, magnesium and strontium to penetrate the skin.
4. The combined action, thermal and chemical, is considered responsible for the therapeutic effect.
5. There is continuous supervision, to maintain hydration and monitor blood pressure.

There is also the local tradition, far older than any clinical centre: sand baths taken on the beach itself during the hottest hours, a practice generations of Madeirans and Porto Santo residents know from family.

What the research shows, and what it does not

Let us be precise, because this is where most writing on the subject overreaches.

What is supported: the physical, chemical and thermal properties of Porto Santo's biogenic carbonate sands have been studied, and psammotherapy is recognised as an adjunct in treating orthopaedic, rheumatic and circulatory problems. The thermotherapeutic effect of heat on joint and muscle pain is itself well established in physical medicine and rehabilitation.

What it is not rigorous to claim: that the sand cures disease, replaces medical treatment, or produces fat loss. Psammotherapy is a complementary therapy, not an alternative to clinical care.

Contraindications to take seriously: intense heat and prolonged sweating are not suitable for everyone. Cardiovascular problems, uncontrolled hypertension, pregnancy and certain dermatological conditions require prior assessment. The rule is simple: speak to your doctor first, and take the treatment at a supervised centre, not on your own initiative on the beach for hours.

When to go

Counterintuitively, peak summer is not the best time. The shoulder seasons, May to June and September to November, offer the best balance: sand and sea still warm, ambient temperature more comfortable for a heat therapy, a calm island and open appointment slots at the centres. It is also why wellness is Porto Santo's strongest argument outside high season, a subject we develop in our article on the island off season.