Beauty obsessives of a certain stature never let little things such as a six-hour plane ride or pesky F.D.A. approvals get in the way of a fresher look. These early adopters have always sought the new and obscure, crossing oceans for a promise, however untested or elusive.

Profhilo is the latest object of desire that’s luring well-heeled Americans to distant shores. Today, the mythical Fountain of Youth flows not out of the earth but through a syringe.

A hyaluronic-acid injectable, Profhilo aims to refine and illuminate the skin, not fill it, the way similar substances do. Stacey Bendet, the founder of the fashion label Alice + Olivia, who had her face shot with Profhilo recently, tells me, “My skin looks like glass, incredibly clear. I saw a change five or so days after my first treatment—my skin felt dewy and fresh. It’s a really big game changer.”

Benjamin Puckey, a leading makeup artist, heard about the new injections from a number of his high-profile clients. Some of them have partaken in the U.K. or the Netherlands and raved about how Profhilo makes their face more hydrated and firmer without changing its natural contours.

While buzz has been building around Profhilo since 2015, when it launched in Europe, the injectable hasn’t been approved yet by the U.S. Food and Drug Administration, a process that can take years. Long, tedious, wrinkle-accumulating years.

Ah, but it turns out some resourceful beauty enthusiasts have found a way to score Profhilo without fueling up the jet.

For months, I’d been hearing whispers of Manhattan- and Los Angeles–based doctors procuring Profhilo from overseas sources and discreetly offering it to selected patients. Several doctors corroborated the rumors. “There are definitely people doing Profhilo here who are getting it from Europe,” a SoHo-based dermatologist told me. But no one was willing to name names.

“My skin looks like glass, incredibly clear.”

A friend in Beverly Hills who manages a plastic surgeon’s social-media accounts alleged that a nurse practitioner in West Hollywood was offering Profhilo in secret.

I chatted with the person in question, who was lovely, but she denied administering the injections. She did tell me that her European and bi-coastal patients ask about Profhilo—she calls it a “deep hydrator”—and that she may eventually add it to her armamentarium “to be ahead of the game,” she said. She doesn’t regard the missing F.D.A. approval as a roadblock of any kind.

In fact, she likened the use of unapproved Profhilo to the common practice among medical providers of administering F.D.A.-vetted products “off label.”

But according to Patrick Armstrong O’Brien, a legal coordinator for the American Med Spa Association, the situation with Profhilo is quite different from the off-label uses of green-lit injectables, such as Botox or Restylane. As he explains, “When an F.D.A.-approved medicine is used in an unapproved way, it is referred to as ‘off label.’” (An example would be injecting a substance in the lips when it’s only indicated for the forehead.) “But if a substance isn’t approved at all, there is no ‘label’ to go ‘off’ from—meaning the substance has no F.D.A. authorization for any human medical use,” adds O’Brien. “This is not to say that medicines and fillers that are legal in Europe but not here are unsafe; it only means that their safety has not yet been determined by the F.D.A.”

Nevertheless, the Fuel Stop, a medical spa on New York’s Central Park South, boldly touts Profhilo on its Web site, enumerating its attributes as “reversing the signs of aging at a cellular level, stimulating new collagen and elastin cells, significantly improving the appearance of fine lines and wrinkles, and giving you firmer, more youthful skin on your face.” The spa’s founder is a nutritionist who, cryptically, lists only her first name and last initial on the company site.

A talented dermatologist based in Manhattan told me, “I had an Italian doc come to my office and teach [Profhilo injections] to me. He brought a few boxes. I asked him because I was getting so many requests.”

This dermatologist agreed to share more in exchange for anonymity. He and his patients are well known, and revealing his identity could jeopardize his reputation and his medical license.

It started last summer, he said, when a handful of longtime patients—a mix of “Hollywood types and very wealthy Upper East Siders”—began inquiring about Profhilo after hearing about it from friends in London and Paris. One of his regulars, an eager socialite, actually went to The Fuel Stop for the injections. “I almost felt like if I didn’t ramp up my Profhilo work, I was going to start losing people,” he confided.

Once this doctor learned the recommended five-point injection technique for Profhilo, he began treating his inner circle—“only those I trust and have been seeing for some time,” he said. Usually, doctors administer two rounds of Profhilo one month apart, and they say the effects can last for four to six months. The cost of an average session, he says, is $800. His Profhilo supply is replenished only when the Italian doctor pays him a visit.

Because of the product’s scarcity in the U.S., enthusiastic Profhilo fans have had to find a work-around. “I had friends hand-carry it back from Europe,” says Bendet. (Apparently that’s a thing: people buy Profhilo from doctors abroad and bring it back to the U.S.)

Profhilo loyalists consider the substance to be a sort of non-filler, because it doesn’t add volume or puff up the face. Its chemistry is different from the multiple F.D.A.-approved hyaluronic fillers currently on the market. With Restylane and Juvéderm, for instance, the hyaluronic-acid molecules are bound with a chemical to increase their strength and longevity. Profhilo is formulated without these cross-linking chemicals. Instead, it’s heat-stabilized. The process gives the hyaluronic acid a honey-like fluidity, allowing it to spread through the dermis, grabbing water to smooth the skin. Some data also suggest that Profhilo can encourage collagen and elastin synthesis, but the studies are company-funded and not entirely conclusive.

Profhilo’s hyaluronic acid has honey-like fluidity. As it spreads throughout the dermis, it grabs water molecules, making the skin appear even smoother.

Naturally, some doctors are skeptical about the wonders of Profhilo. “There is no evidence in my mind, none, that it actually helps build collagen, helps lubricate… I just don’t see it,” says Dr. Ellen Gendler, a board-certified dermatologist in New York City. “It seems to be … I’m going to call it ‘a rich person’s treatment.’” (A representative from Profhilo did not respond to Air Mail’s questions in time for publication.)

While Dr. Robert Anolik, a board-certified dermatologist in New York, believes that “part of the benefits expected from Profhilo is a smoother, firmer skin appearance from the hyaluronic-acid hydration,” he won’t be breaking any rules in the name of moisture. “Hearing that some doctors are quietly offering Profhilo before it’s F.D.A.-approved makes me loudly cringe,” he says.

Dermatologists are generally a by-the-book bunch, unnerved by the unsanctioned.

“A lot of us will say, ‘Well, it’s been used in Europe for so many years, and the F.D.A. is really slow,’ and that might be the case,” Dr. Gendler tells me. “But they do some pretty rigorous trials before they let someone get treated with an injectable.”

As with any injection, complications from Profhilo are possible. Some common side effects are bugbite-like swelling and bruising at the injection sites, which subside over time. If accidentally injected into an artery, the gel can block blood flow to the skin or eyes, inviting all manner of trouble, from skin necrosis (tissue death) to related scarring to blindness. Adept doctors can usually avert catastrophe by injecting the enzyme hyaluronidase at the first sign of anything out of the ordinary.

While our anonymous doctor believes Profhilo is “very safe,” he says he discloses the risks and benefits to his patients, making it explicitly clear that the product is not F.D.A.-approved. He claims that the majority of them “don’t seem to care” about that last part.

Curious about the liability he might be assuming, I reached out to Jillian R. Subbio, the in-house counsel to her husband’s practice, Subbio Plastic Surgery & Medspa, near Philadelphia. As she explains, “Injecting an unapproved [filler] is not illegal, per se, as the F.D.A. does not regulate the practice of medicine.” But to be safe, providers should be able to show that the product is “being used to treat a serious condition for which there is no effective alternative approved for treatment,” she adds. “And that’s really hard to do with a cosmetic injectable.

Indeed, lifeless skin is hardly as dire as it sounds.

If reported to the state medical board or hit with a malpractice suit, a medical doctor may be subject to an investigation, which could result in the suspension or loss of his or her medical license—no matter how bulletproof their consent forms.

But for a certain set of people, Profhilo’s unavailability and its illicit air may be part of its appeal—at least until something more provocative comes along.

And just like that, I heard from Puckey, my makeup-artist informant. “I was speaking to my friend in London about Profhilo,” he tells me, “and she said she now prefers Juvenus, because it makes her less puffy. Have you heard of this one?”

Jolene Edgar is a writer who frequently contributes to Town & Country, Allure, and Harper’s Bazaar