Perfectly circular bruises are adorning the bodies of Olympians in Rio this summer -- particularly among swimmers such as Michel Phelps (pictured) -- after the sudden popularity of cupping, an ancient therapy practiced as far back at the 6th century. But this is one of many treatments used throughout history that aimed to control the flow of fluid within the body.
CNN spoke to Claudia Stein, professor of history at the University of Warwick, England, and Laurence Totelin, a historian of medicine at Cardiff University, Wales, to find out more about cupping and some of the more gruesome, but surprisingly commonplace, medical practices used to treat ailments throughout history.
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Cupping therapy has been practiced from as early as the 6th century, according to Totelin, and is seeing a comeback today through the increased popularity of traditional medicine. "Globalization of medicine is attracting Western people to this holistic practice," says Stein.
The practice involves cups placed on specific regions of the body to create suction and encourage blood flow. Practitioners believe it promotes healing for a broad range of ailments in a similar way to the premise of bloodletting and leeching -- the goal being to balance levels of blood inside the body.
"Cupping was more common," says Totelin about the treatment which is still practiced today in Chinese medicine. In ancient times, however, its use was part of everyday life. "Cupping is one of the big things you do ... to be healthy," adds Stein. "[People would] place a cup to draw blood out of the body or to prevent getting sick."
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Bloodletting is one of the oldest known medical practices and is thought to have begun with the ancient Egyptians. This ancient practice involved the drawing -- or letting -- of blood from the body, which was believed to balance an individual's fluid levels.
Many ancient therapies were based on the belief that the human body consisted of four fluids -- or humors -- blood, phlegm, black bile and yellow bile. If their levels were thought to be out of sync, a range of unpleasant treatments were used to restore them.
The procedure came with strict rules and restrictions, with cuts only being made at specific points on the body. "It was a very complicated practice," says Stein.
"You would bloodlet if you have too much blood," says Totelin. The symptoms of excessive blood varied between individuals and genders, with females thought to be imbalanced if their menstrual cycles were disrupted, or delayed, and males if they were low on energy and sluggish, Totelin explains.
However, bloodletting was also practiced regularly at specific times of year in order to simply stay healthy -- such as in the springtime, when blood was thought to be thinner, according to Stein. "[People] used bloodletting in certain seasons to give a fresh start into their year," she explains.
Among its key ingredients was oxgall (bile from a cow's stomach) -- perhaps not the nicest thing to rub in your eye, but far more pleasant than many of the grisly treatments from medicine's murky past.
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These blood-sucking worms were used in a similar way to bloodletting but provided a more localized way of extracting excess blood from the body. "You put leeches on the blood to draw bad fluid," says Stein.
The animals have evolved for optimal blood extraction from humans and release hirudin -- an anticoagulant -- during feedings to enhance blood flow.
Their use can be traced back to ancient Indian Ayurveda practices and leeches are still sometimes used in modern medicine to restore circulation after surgery.
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Dating back before ancient Roman and Greek times, according to Totelin, holes were drilled into human skulls to relieve a range of ailments from migraines to head injuries.
The practice -- known as trepanation -- is considered by experts to be the oldest form of neurosurgery. Its original use was to relieve pressure, reduce swelling and also enhance overall bloodflow in the brain and improve well-being.
The premise behind the practice is still used by neurosurgeons today to reduce swelling and pressure in the brain before, or after, surgery.
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For centuries, this poisonous chemical was taken in a range of forms -- pills, ointments, and inhalation. The one thing they all had in common was that they came with extensive, and long-lived, side effects including kidney failure, mouth ulcers and teeth loss. "We now know it was mercury poisoning," says Stein.
But the poison was considered an effective remedy, particularly against skin diseases. "Mercury was used for everything relating to skin diseases until the late 19th century," says Stein. It was also among the first treatments used against syphilis.
Mercury was believed to help people sweat and salivate, in line with the belief of restoring fluid levels inside the body to treat ailments. One treatment involved rubbing patients with mercury ointment and locking them in a secluded, stuffy room to promote sweating. "[It was] seen as a sign of the body healing itself by getting fluids out," says Stein.
Many people died from mercury poisoning, rather than the disease it was meant to cure. This 19th-century illustration shows "part of the face destroyed by [syphilis] and the baneful effects of mercury."