Cupping involves heating the air inside a glass cup, inverting it, and placing it on a body part, usually the back or stomach. This creates a vacuum, which binds the cup to the body and sucks the skin upward for about 10 minutes.

Practitioners claim there are various benefits. Some of these are impossibly vague or even nonexistent, and include unblocking chi, restoring health, or improving circulation. There are also claims it can activate the lymphatic system or clear the colon. But if your lymphatic system and colon are misfiring, you need much more than a rudimentary sucking device and a chanting shaman in superfluous beads who burns incense and plays Ancient Future CDs.

Other supposed benefits are the ability to cure depression, arthritis, influenza, migraines, infertility, insomnia, herpes, cramps, asthma, and cellulite cancer. There is no research to support any of this, but there is strong evidence that cupping causes pain, excessive fluid accumulation, and purple skin from ruptured blood vessels.

Forms of cupping were used by ancient peoples in China, North America, Assyria, Greece, and Egypt, and this history is usually touted by its practitioners. Of course, where and when a technique was used is unrelated to its efficiency, and there is no science that supports cupping’s claims, which contradict our knowledge of anatomy and physiology, as well as of Germ Theory.

Those who favor the Chinese version usually combine cupping with acupuncture and place the cup on supposed meridian points, whose locations vary by practitioner. Another tactic is to use cupping in conjunction with a massage, the latter of which can speed muscle healing and reduce tissue inflammation. By conflating the massage with cupping, the benefit can be given to the wrong technique. When coupled with an implied ancient wisdom, this can convince some patients that it works.

This alternative medicine itself has an alternative, wet cupping, in which the skin is punctured before the cup is emplaced. The negative pressure then draws out blood, so this procedure is little more than bloodletting that incorporates a heat source. The goal is to suck toxins from the body, though practitioners never specify what toxins are extracted, nor do they explain how low pressure would cause sweat glands to secrete toxins instead of sweat. In fact, the only way this technique will work is if it’s used on poison dart frogs.