Massage clients report bizarre flu-like reaction after popular spa treatment

A popular wellness treatment is allegedly leaving some people with unexpected symptoms, including aches, fatigue and headaches.

Social media users have described feeling under the weather after getting a massage, with some saying they feel as though they are coming down with an illness.

The reaction is sometimes referred to online as "massage flu," though health experts say it is not an actual medical diagnosis.

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"This phenomenon is something I have definitely heard of and had patients tell me," W. Zach Smith, a Seattle-based physical therapist and co-founder of HIDEF Physical Therapy, told Fox News Digital.

"The idea of this has been around a long time but usually described as fatigue and soreness," Smith said. "The flu part of the name I have heard more recently."

Soreness can happen when a lot of pressure is applied to the muscles for a long period of time, especially if someone is not used to getting massages, Smith added.

"Any time you go in and apply a lot of pressure to a muscle for a long period of time, it can essentially bruise the tissue," he said.

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The body may also have a mild inflammatory response after a massage, which can contribute to soreness, Smith said.

Drew Voelsch, a chiropractor at Forza Chiropractic in Illinois, said he has also heard patients refer to the reaction as "massage flu" or an "adjustment hangover."

"The symptoms are real," Voelsch told Fox News Digital, pointing to soreness, fatigue and mild headaches that may last 24 to 48 hours. "The label is social media."

A massage around the neck, scalp or jaw can also trigger headaches because those areas can be involved in tension headaches, according to Smith.

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Both experts pushed back on the idea that these symptoms are caused by a massage "releasing toxins" from the body, a claim that has circulated in social media comments.

"This is a myth," Smith said. "There is no basis or science behind this."

Voelsch agreed, noting that the liver and kidneys handle the body's waste-removal processes.

To help reduce discomfort, Smith recommended asking for less pressure or a shorter massage and gradually working up to deeper or longer sessions.

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Voelsch also suggested drinking water, eating something light beforehand and moving gently afterward.

Mild soreness is typically not a cause for concern, but Smith said new or persistent pain may be a reason to contact a doctor.

"If you are having a new, unexplained pain that is persistent, that would be a good time to call your doctor," he said.

Voelsch recommended seeking medical advice if symptoms last longer than about 72 hours or include fever, sharp or radiating pain, numbness or tingling, spreading swelling or bruising, or faintness.