The sight of Michael Phelps hauling in swimming gold medals while covered in marks from ‘cupping therapy’ has generated a couple of enquiries asking if we “do this kind of massage”. We don’t – it’s a Chinese medicine technique not a Thai massage technique. But it got us curious: we didn’t know how it worked, if it worked, or even if it was a massage at all.

So what is it? The idea is that glass or plastic cups are placed on the subject’s skin, and a vacuum induced in the cup (in modern methods by pumping air manually out of the cup through a valve at the top; in traditional methods by heating the air in the cup and allowing it to cool on the skin). The result either way is that the skin is sucked upwards into the cup.

The traditional Chinese wisdom is that this suction draws toxins out of the body and stimulates the flow of Qi to the focus area. In practice what happens is that the small blood vessels in the skin are ruptured and the resulting blood clots, leaving the dark coloured mark, which lasts several days (and which were visible all over Michael Phelps).

This sounded a little suspect to us, so we looked for some scientific evidence. Edzard Ernst’s review of systematic reviews concluded: “The effectiveness of cupping is currently not well-documented for most conditions. This is in sharp contrast to the many claims made by the proponents of this therapeutic modality, including those practising traditional Chinese medicine or complementary and alternative medicine”.

A second systematic review concluded “current evidence is not sufficient to allow recommendation for clinical use of cupping therapy for the treatment of above diseases ... in people of any age group”.

So, no evidence that cupping works for any condition, in any people. Yet Phelps is not the only one. Jennifer Aniston and Gwyneth Paltrow are fully paid up cuppers too, and the treatment is widely available in London. We think what they are seeing is just a strong placebo effect, with all the allure of a ‘centuries old technique’.

With so many celebrity endorsements, would we recommend trying it? It could work as an incredibly elaborate way to conceal an embarrassing hickey. As long as you’re not diverting your spending from treatments with more proven results (traditional medicine, complimentary medicine or otherwise), then we can’t see how it can hurt. Apart from the embarrassment of the blotches on your back of course!

If only Thai massage left visible scars on elite athletes, we would be inundated with calls!