A Woman Fell Asleep During Cupping Therapy. She Woke Up with Bizarre Blisters.
A woman developed a collection of large blisters in the shape of a circle from cupping therapy. The injury occurred because she applied the cups herself and then fell asleep, leaving the cups on for too long. (The indentation at the center of the circle is likely due to the cupping vacuum mechanism).
Credit: Reproduced with permission from JAMA Dermatology. 2018. doi:10.1001/jamadermatol.2018.3277. Copyright© 2018 American Medical Association. All rights reserved.

When you think of cupping therapy, large circular bruises might come to mind. Indeed, the bruises are often a side effect of the alternative-medicine technique, which involves attaching circular cups to the skin using suction.

Generally, cupping therapy is fairly safe, but for a woman in California, the experience left her with a rather painful remnant: a collection of large blisters in the shape of a neat circle. The injury occurred because she had applied the cups herself, and then fell asleep, according to a new report of her case.

The woman, who is in her 60s, had recently fallen and hurt her shoulder. To try to treat the injury, she decided to try dry cupping therapy, Supporters of the treatment say the suction increases blood flow to the area, which, in turn, reduces muscle tension and inflammation, and promotes healing. [27 Oddest Medical Case Reports]

The suction is created either by heating the cup inside (which forms a vacuum) or by using a handheld pump. The cups are usually placed on the skin for 5 to 15 minutes, according to Healthline.

In the woman's case, she used a handheld pump to apply the cups to her body, according to the report, published today (Dec. 12) in the journal JAMA Dermatology. But she fell asleep after she applied the cups, and woke up 30 minutes later. She immediately noticed large, painful blisters in a circular pattern in the area where the cups had been.

The blisters formed because the suction damaged the patient's skin. "The vacuum was strong enough to split the skin, separating the normal two [top and bottom] layers of skin," said case report co-author Dr. Maria Wei, a professor of dermatology at the University of California, San Francisco.

If properly performed, cupping therapy should not cause blisters, Wei told Live Science. But in this case, the device was left unsupervised, causing "too strong of a vacuum" and damaging the skin, Wei said.

"This case illustrates the need for supervision while performing cupping with a mechanical device" such as a pump, said Wei, who treated the woman. "If properly monitored, it shouldn't be a problem."

Cupping therapy gained international attention during the 2016 Summer Olympics when several athletes, including champion swimmer Michael Phelps, were seen sporting circular bruises on their bodies from having undergone the therapy. (The bruises, which are a known side effect, occur when the suction causes small blood vessels to burst.)

Although many athletes say they've experienced benefits from the therapy, there are few rigorous scientific studies on the topic, and it's unclear if the treatments' perceived benefits could be due to the placebo effect, Live Science previously reported.

Wei said she and her colleague decided to publish the image to alert users and physicians to this potential side effect of blisters.

Since the blisters were causing the patient discomfort, doctors drained the blisters and applied petroleum jelly to the area under a sterile dressing, the report said.

Originally published on Live Science.