It was, perhaps, inevitable in 2022 that TikTok users would figure out how an of-the-moment slicked-back bun could double as a self-care moment — and just as inevitable that the multitasking hairstyle would go viral.

Hence the Olaplex bun, where the “slick” of the bun comes from Olaplex No. 3, No. 6 or No. 7, hair treatments whose users are so evangelical that they tweet things like “Tempted to put Olaplex down as my religion on the census form.” By February, the hashtag #Olaplexbun had more than five million views.

The hashtag/hairstyle wasn’t created by Olaplex, said JuE Wong, its chief executive, though the company soon posted its own tutorial suggesting a cocktail of multiple products. “What started out as a treatment has transformed into a lifestyle accessory,” the company said on its website.

Fair enough. Olaplex has grown from three products made by hand in a surfboard-littered garage in Santa Barbara, Calif., in 2014 into a salon essential and a much-posted-about (and expensive) staple of millions of women’s at-home hair-care routines, among them Kim Kardashian, Drew Barrymore and Jennifer Lopez. Along the way, the company — its hero ingredient is said to repair hair and prevent damage from bleaching and dyeing — spawned many imitators and became shorthand. (There are now pretenders for the crown of “the Olaplex of nail care” and “the Olaplex of skin care.”)

In 2021, Olaplex knocked Dyson off its perch as hottest hair brand in a report by the shopping site Cosmetify. Its 2022 rankings have not been released, but Matt Davies, the managing director, wrote in an email that the Olaplex “will still come out on top. We sell every product, every day (stock permitting), and often have customers purchasing the complete collection despite the price.” (That’s about $225.)

In September 2021, Olaplex went public and was valued at more than $14 billion.

But for all the customers who think the products are capable of necromancing their hair, there is also dissent: unhappy customers, skeptical chemists, disillusioned colorists. Sephora.com has dozens of one-star reviews for Olaplex, some blaming the oils and creams for damage, many just saying the products don’t live up to the hype.

Ms. Wong, in a statement, said the company understood there may be “naysayers,” but that Olaplex “created the bond building category and is the leader in prestige hair care.”

Every beauty brand engages in puffery to sell products. Olaplex has just been phenomenally successful at it.

“That it cures hair breakage sounded outlandish, so you had to try it,” said James Miju, a colorist in downtown Los Angeles, who first got his hands on Olaplex when it was still being made by hand in the garage, with every batch a different shade of yellow and the bottles not filled uniformly. He thinks its benefits are “exaggerated, but it still defies everything you think you know about hair.” (Mr. Miju uses the Olaplex professional product, which is added to color or bleach, only where he thinks it works best: relatively fast procedures involving thin-ish hair without too much damage.)

In late 2014, Dean Christal, the serial entrepreneur who founded Olaplex with his wife, Darcy, posted prolifically on a hair dye forum where mostly professionals were questioning the new line. He responded in a series of 22 posts to every point raised. When people commented about his 22 posts, he wrote another 11 posts.

In response to the lack of information about how, specifically, Olaplex works, he wrote: “We are a small company and it’s us against the world that wants to copy our formula.” Barely two years later, Olaplex was suing L’Oréal for, among other things, allegedly infringing two patents and misappropriating trade secrets, after L’Oréal had met with Olaplex about possibly acquiring the company.

A jury initially awarded Olaplex $100 million, but the trial judge slashed that to $66 million. An appeals court then threw the ruling out and remanded some of the claims to Delaware federal court for a new trial. (The case has since been settled to “mutual satisfaction,” Ms. Wong said, though she cannot discuss it the terms.)

Hair Is Complicated

The bulk of hair is keratin, which is made up of alpha helixes, or twisted ladders of protein held together by disulfide bonds. Those bonds largely determine both the hair’s strength and its curl factor (more bonds equal more curl). Those same bonds are damaged by things like color, perming and heat styling, as well as the mechanical stress of brushing and combing.

Olaplex’s claim is that it repairs the disulfide bonds, thanks to a hero molecule called bis-aminopropyl diglycol dimaleate — clearly not named by a marketing team. Technically, the repair claim may be an overstatement: Olaplex doesn’t fuse broken bonds but instead creates a different kind of bond, said Joseph A. Schwarcz, a chemist and the director of the McGill University Office for Science and Society. (Dr. Schwarcz nonetheless pronounced Olaplex “a clever concept.”)

Perry Romanowski, a cosmetic chemist and a founder of Thebeautybrains.com, a website and podcast on which scientists examine product ingredients and industry promises, was skeptical of Olaplex’s claims. The company’s top-selling product, its No. 3 Hair Perfector, says on the label that it is “NOT a conditioner” (capital letters are Olaplex’s); it’s designed to be used before shampoo and rinsed out.

Yet Mr. Romanowski pointed out that many of its ingredients are standard conditioning agents. They’re likely responsible for the shine, smoothness and “manageability” Olaplex touts, he wrote in an email.

“I suspect that if the Olaplex hero ingredient was left out of the No. 3 product, no one would really notice the difference in performance,” he added.

Emaly Baum, a colorist whose clients include Scarlett Johansson, suggested that one reason for Olaplex’s results may well be the routine people have developed around using it.

“If you’re using Olaplex, you’re probably doing other things to focus on your hair health, like washing it less,” said Ms. Baum, the owner of Beauty Supply salon in SoHo. “It makes sense that if you have a diligent care plan, your hair would get better.” (Ms. Baum said she has “a complicated relationship” with Olaplex but uses it occasionally on clients.)

None of the chemists The New York Times interviewed could find ingredients in Olaplex formulas that might cause the breakage some reviewers have described. Several colorists pointed out that people who use Olaplex often have damaged hair in the first place, so what happens may not be caused by the product.

Hair that has been lightened — particularly in a dramatic transformation, like dark brown to platinum blond — is very fragile when it’s wet. “A lot of breakage after lightening happens just in the way people handle their hair,” said Cara Craig, a colorist at Suite Caroline in SoHo.

The Elusive Origin Story

Olaplex’s origin story is hard to pin down. Few accounts — even of how Mr. Christal met Craig Hawker, a University of California, Santa Barbara chemistry professor, say — are the same. One of the only constants is that Dr. Hawker, a former researcher at IBM’s innovation lab whose patents have formed the basis of at least 10 companies across a variety of industries, enlisted his former graduate student Eric Pressly, whose garage was the birthplace of the first batches of Olaplex.

Dr. Pressly’s spokeswoman abruptly canceled a scheduled interview after I sent questions she had requested. She said they were “too detailed.” Dr. Hawker requested questions via email and then did not reply. Mr. Christal did not respond to interview requests. (Neither of the scientists was ever directly employed by the company, Ms. Wong said, and Mr. Christal is no longer there. In 2019, the private equity firm Advent International acquired Olaplex for an undisclosed sum.)

The first Olaplex product was an in-salon treatment that looked like beer and smelled like wood but was essentially the hero molecule mixed with water, said stylists who used it at the time. Mr. Christal took a sample to the colorist Tracey Cunningham in Beverly Hills, he told Modern Salon, “and she used it the next day on Gwyneth Paltrow and Jennifer Lopez.”

Ms. Cunningham, today one of the company’s 10 brand ambassadors, did not answer questions about whether she usually tests unknown products on celebrities. She did use the Olaplex the next day but, she wrote in an email, on the actress Angela Featherstone, who’d recently gone from blond to red and wanted her “obviously damaged and compromised” hair to be blond again.

“From that morning on, I’ve never not used it on my clients,” Ms. Cunningham wrote.

Early on, the brand recognized the power of hairstylists like Ms. Cunningham, and worked to cultivate it. It was Ms. Cunningham, her spokeswoman said, who first used the product on Ms. Kardashian, who then told the 1,800 or so people at a beauty master class in 2015 that sleeping with Olaplex on her hair “really works.” By then, the brand, barely a year old, had already generated more than $14 million in sales through just one distributor. (Later that year, the Christals bought the investment banker Bruce Wasserstein’s mansion in Santa Barbara.)

Ms. Wong, who became chief executive in 2020, said that Ms. Kardashian was not paid and that the brand does not pay for its celebrity endorsements. Instead, it lavishes its attention on its brand ambassadors, who are paid (though not “full-time job money,” Ms. Wong said). There are also 153 brand advocates — self-styled “hairapists,” among others — who aren’t paid “financially,” Ms. Wong said, but with products and content-sharing arrangements.

Olaplex’s strategy was a winner. The company’s products are the kind of thing people come into the salon and ask for by name.

“I’d never seen that before Olaplex,” Ms. Craig said.

Salons can charge for both the professional treatments and the retail products. Mr. Miju said that at one point, Salon Republic in West Hollywood, his former, salon was making about $8,000 a month in Olaplex profits alone, with four or five full-time hairstylists ensuring that “every customer would leave with a product.” Salons can’t make as much from Olaplex since its debut at Sephora in 2018 and then Ulta salons in 2021 (it is now available in Ulta stores), where it’s usually more convenient — and cheaper — to buy.

The proliferation has gone over well. Consider Amanda Lauren, an interiors stylist in Los Angeles in her 30s, whose devotion to her hourslong Olaplex routine (“the only way to have decent hair days multiple days in a row,” she said) is such that she began ordering the treatments online before trips to the Hamptons.

“At least now there’s an Ulta in Bridgehampton,,” Ms. Lauren said, so she’s not out of luck if the mail is late.

Bad Hair Days

Earlier this year, the same platforms that helped turn Olaplex into a household name hosted far less friendly content: A TikTok video that went viral said that the European Union and Britain would ban Olaplex No. 3 for containing lilial, an ingredient used in trace amounts as a fragrance — and linked to infertility. The company responded quickly, destroying $4.3 million worth of inventory, Ms. Wong said, and announcing a reformulation.

Dr. Schwarcz called the E.U. ban “pushing the science beyond what it should be pushed,” as lilial had been linked to infertility in animals only after they consumed large amounts and no one is likely eating a hair product. “You might as well ban chamomile tea,” he said. (It naturally contains lilial.)

Still, the company remains secretive, even by beauty company standards. It would not allow access to any scientists or make Ms. Wong available until I had submitted written questions. Nor would it specify when it would be out of the quiet period the Securities and Exchange Commission imposes around releases of earnings and thus whether anyone would speak at all. A company spokeswoman joined the Zoom call with Ms. Wong and interjected frequently.

When I asked Ms. Wong how she copes, as the chief executive of a hair-care company, when she is having a bad hair day, the spokeswoman assured me that Ms. Wong never has such days.

When I asked what the biggest misconception about Olaplex was, Ms. Wong’s message was for investors, not customers: “Don’t try to understand us with a current sort of business lens,” she said. (Among other things, Olaplex has been a remote workplace since its founding. Of the company’s roughly 145 employees, only the 14 or so who work in research and development have anywhere to go: a 10,000-square-foot facility on the Pfizer campus in northern New Jersey.)

In a filing to go public last year, the company hinted at an expansion into skin care, noting that many of its 80 patents would be applicable and that as a business, Olaplex had options.

The company may need them. Some stylists note that there are several Olaplex competitors, like Wella BlondorPlex, which was introduced in 2020 and includes a bond builder already mixed in with the color. Many also favor K18, another bond-building treatment that takes just minutes and doesn’t need to be rinsed out or repeated as often.

Mariel Loveland, the frontwoman of the indie pop band Best Ex, began using Olaplex in 2014 after she dyed her almost black hair platinum blond, and, she said, the product is “the only thing that kept my hair from being totally horrifying.”

But after nearly a decade of allegiance to Olaplex, Ms. Loveland, her hair often strawlike from bleaching, has found herself increasingly tempted by Instagram ads for a product even more expensive than Olaplex: the K18 Leave-In Molecular Repair Hair Mask. She’s (mostly) made the switch.

“It’s the only thing that’s restored my curl pattern, and my hair feels almost completely normal,” she said of the K18. She sounded incredulous: “Enough for me to buy a $75 cream.”