With a 2,000-year history, traditional Chinese medicine offers a variety of methods for treating illness and injury. Cupping is often associated with the trend, but it has an even longer history.

One of the oldest medical texts in the world, the Ebers Papyrus, describes how ancient Egyptians used cupping for a variety of ailments as far back as 1550 B.C. Prophet Muhammad approved of it in his writings and Hippocrates detailed cupping in Greek culture. It has been used in Sweden for more than 500 years, usually as part of the sauna experience. Recently, cupping has been popular with athletes competing in the 2016 Summer Olympics in Rio, reports CNN. U.S. swimmer Michael Phelps, U.S. gymnast Alex Naddour and Belarus swimmer Pavel Sankovich are fans and have been photographed with spotted backs and limbs.

Michael Phelps at the 2016 Summer Olympics in Rio People were very curious about the circles left by cupping on Michael Phelps' shoulders at the 2016 Summer Olympics. (Photo: Ryan Pierse /Getty Images)

How it works is straightforward: Cups made of glass, ceramic or sometimes bamboo are heated and placed on the skin. As the air inside the cups cools, it creates a vacuum and then an upward suction, pulling the skin into the cup. The cups are left on for anywhere from five to 10 minutes and then removed. This is dry cupping.

Sometimes, a rubber cup and a pump are used for a milder effect that can also be used as a type of massage. Occasionally, large dark circles that look like bruises can occur at the site of the cupping. (They are broken capillaries, not the bruises you see from blunt-force trauma.) Sometimes there are no visible effects, depending on the person, their skin and their ailment.

Wet cupping is a similar procedure, but the skin is cut superficially at the site of cupping and drained of fluid or blood. Then the cut is sterilized and bandaged.

Here's a video that shows how cupping is done:

Why cupping can be effective isn't clear, but several studies have shown that it may be helpful for certain health issues.

In a 2012 review of the efficacy of cupping therapy in PLOS One, researchers looked at 135 randomized controlled trials that took place over a decade or so and threw out many of the studies that they deemed to be poor. They found that, "...our meta-analysis revealed that cupping therapy combined with other treatments, such as acupuncture or medications, showed significant benefit over other treatments alone in effecting a cure for herpes zoster, acne, facial paralysis, and cervical spondylosis."

The researchers didn't find any evidence in existing studies that cupping is good for some of the other issues for which it's used — though there are ongoing tests to check the efficacy of it for everything from hypertension to stroke rehab, blood disorders to fertility problems. The most promising is the area of temporary pain relief. Some studies show it offered significant pain reduction following knee surgery and for lower back pain.

While more research is being done, cupping seems to be one of those treatments that for most people might help and won't hurt. (Of course you should check to ensure that your own health history doesn't preclude taking advantage of the practice. For example, cupping shouldn't be done on the abdominal or sacral regions of pregnant women.) There are some positive results, especially when cupping is combined with acupuncture, so you'll have to find out if it works for you.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.