The treatment has been popular, she said, attracting six to 10 clients a week, many of whom travel an hour or more to the medical spa since the treatment is not widely available. A handful of medical spas and wellness centers offer the service in New York and other major cities, but patients posting in online forums say it is difficult to find providers.

In Atlanta, Dr. Ava Bell-Taylor said her wellness and aesthetics center, the Taylor Medical Group, sees dozens of patients a day for glutathione skin lightening. Many clients tell her they used to fly out of the country until American doctors started offering this service in the last few years.

Treatments involve anywhere from 1,500 to 4,000 milligrams of glutathione, often combined with vitamin C, administered once or twice a week. Each session can cost $150 to $400, depending on dosage and location. Some medical spas recommend 10 treatments, while others say as many as 30 could be necessary to see the desired result. IVs are administered by nurses or doctors.

Even once the skin is lightened, patients have to come back every few months for maintenance. As the glutathione levels fade, so do the effects.

In the Philippines, glutathione treatments are often delivered by people not trained in IV administration, and at higher doses with greater frequency.

Proponents of glutathione in the United States say that’s why patients there see serious side effects, while those in America don’t.

Lakeyshya Brown, a registered nurse who administers glutathione treatments at Lavish Laser, said that in other countries, the glutathione solutions might be mixed with other substances that could cause unintended side effects. It may also be delivered by aestheticians who are not trained in IVs and injections, increasing the risk that a patient could become infected or be injected with air, leading to a potentially fatal embolism.