In recent years, cryotherapy has been increasing in popularity. The treatments have been used worldwide but are relatively new in the United States. The machines used for cryotherapy subject users to subzero temperatures. The treatments generally consist of two- to four-minute exposures to temperatures ranging from minus 166 to minus 319 degrees in a small enclosed chamber.

Cryotherapy providers say that the treatments can reduce pain and inflammation, increase and improve blood flow and help with weight loss. Cryotherapy is also said to reduce aging, improve skin texture and resilience, and even ward off depression. Celebrities and sports stars have endorsed the use of the treatments as an alternative to traditional ice baths.

However, some health experts are saying that the treatments are unproven and that users may be putting their health at risk by undergoing them. Chelsea Ake-Salvacion recently died of asphyxia while in a cryotherapy machine at a spa in Henderson, Nevada. Ake-Salvacion, 24, was in a machine at the Rejuvenice spa, where she worked, when she succumbed to low oxygen levels and accidentally died of asphyxia. She was found dead on October 20.

Nevada has since created new health guidelines for cryotherapy providers in the state. The new guidelines state that cryotherapy machines should not be used by anyone younger than the age of 18 or anyone that is under five feet tall. The treatments are also prohibited for anyone suffering from certain health conditions, including a history of stroke, high blood pressure, seizures, infections, or claustrophobia. The health conditions also include pregnancy or having a pacemaker.

The guidelines from the state health department also recommends that users should have only one session per day for no more than three minutes. Users should also have their blood pressure taken before and after the cryotherapy session. Cryotherapy centers are asked to have nitrogen monitors in the rooms, as well as emergency kits and defibrillators on site. The new guidelines were announced on Friday. The state’s chief medical officer likened them to the ones in place for sauna use.

The federal Food and Drug Administration has not approved cryotherapy for medical use. Liquid nitrogen has long been used medically for things like wart removal, but the medical and scientific communities have acknowledged that there a lack of evidence of the benefits of full-body exposure. The health department in Nevada has said it will work with other agencies and businesses to ensure that the new guidelines are followed.