The pain reliever Tylenol is a classic American brand, with tens of millions of users and a 70-year history. The company behind it, Kenvue, is just two years old and unknown to most Americans.

The Trump administration is expected on Monday to link Tylenol use during pregnancy to autism, a connection that remains unproven. That has put Kenvue in the spotlight, faced with a growing public relations nightmare for a product that has weathered crises before. Most notably, in the 1980s, Tylenol became the textbook example of how to manage a corporate crisis, after product tampering killed seven people and triggered a nationwide panic.

Johnson & Johnson survived the traumatic episode, rescuing a product it had manufactured for decades. But in 2023, looking toward its more profitable medical businesses, the company spun off Tylenol and other consumer brands into a new business, Kenvue. Based in Summit, N.J., Kenvue also makes other nostalgic and well-known brands, like Band-Aid, Listerine, Neutrogena and Johnson’s Baby Shampoo.

Renewed public attention on Tylenol began early this month, when The Wall Street Journal reported the Trump administration’s plans to release a report tying Tylenol use during pregnancy to autism. The company’s stock has plummeted by 16 percent since then, and was down by 6 percent on Monday.

Melissa Witt, a spokeswoman for Kenvue, said in a statement on Monday that “we believe independent, sound, science clearly shows that taking acetaminophen does not cause autism.” She added, “We strongly disagree with any suggestion otherwise and are deeply concerned with the health risk this poses for expecting mothers.”

Researchers have studied a potential connection for years, but so far the studies have not shown that Tylenol use among pregnant women causes autism.

Kenvue has made repeated attempts to forestall Monday’s announcement, and to try to reassure customers. The company’s interim chief executive, Kirk Perry, met earlier this month with Robert F. Kennedy Jr., the nation’s health secretary, to make the case that there was no link between Tylenol and autism and that the product offered a safe and important way of relieving fevers in pregnant women, according to an account in The Journal.

Ms. Witt confirmed to The New York Times that the company had “engaged in a scientific exchange with the secretary and members of his staff as it relates to the safety of our products.”

This month, the company also added language to the frequently asked questions section of its website seeking to reassure consumers that they should not be “concerned about acetaminophen and autism.”

Tylenol is the best known among some 600 products containing the active ingredient acetaminophen, an analgesic. Each week, nearly a quarter of U.S. adults use a medicine that contains acetaminophen, according to a trade group for consumer health care products.

Even with the generic competition, Tylenol still generates roughly $1 billion in annual sales for Kenvue, according to an estimate from Morningstar, the financial services company. (Kenvue does not report its revenue from Tylenol.)

“Any potential threat to the product could have a noticeable impact on the firm’s earnings power,” Keonhee Kim, a Morningstar analyst, wrote in a note to investors.

Even before Trump officials amplified the issue, Tylenol had been hit with lawsuits from families who claimed that their children were diagnosed with autism or attention deficit hyperactivity disorder after Tylenol use during pregnancy.

Kenvue, along with major retailers that sell their own generic versions, was named a defendant in the litigation. But a federal judge rejected those claims, dismissing them for lack of reliable scientific evidence. The families are appealing the decision.

Far beyond Tylenol, Kenvue has been struggling with its direction as sales have slumped. In July, the company ousted its chief executive, Thibaut Mongon, and replaced him with Mr. Perry, a veteran in the consumer goods business. In recent months, the company has generated interest from activist investors who have pushed for the company to be acquired, or to sell off some of its business lines.

Acetaminophen was first discovered in the 19th century, but it wasn’t until the late 1940s that researchers showed it could reduce pain and lower fevers.

At the time, research was beginning to show safety risks associated with taking too much aspirin, the leading pain reliever on the market. McNeil Laboratories, a family-owned company in Philadelphia, saw an opportunity to market acetaminophen as a safer alternative.

In 1955, McNeil introduced the first Tylenol product, Elixir Tylenol, a liquid for children. McNeil packaged the product like a cartoon fire engine and marketed it as being “for little hotheads.”

In 1959, Johnson & Johnson acquired McNeil. The next year, Tylenol became available over the counter, without a prescription.

Over the years, Tylenol has occasionally been subject to recalls for quality control issues. The product has also weathered a series of debates in the medical community and regulatory proposals about its known side effects, like liver damage, when taken at high levels.

In 2013, an investigation by the news organization ProPublica found that over three decades, Johnson & Johnson’s McNeil unit “repeatedly fought against safety warnings, dosage restrictions and other measures meant to safeguard users of the drug.” (The company said it takes the product’s risks seriously and always acted to mitigate them.)

By far the biggest threat to the product came in 1982, when someone tampered with capsules of Extra-Strength Tylenol, lacing them with cyanide and killing seven people, including a 12-year-old girl, in the Chicago area. No one was ever charged in the deaths, though one suspect, who has since died, was convicted of extortion for sending a letter to Johnson & Johnson promising to stop the killings in exchange for $1 million.

Johnson & Johnson scrambled to respond, regaining public trust by quickly pulling Tylenol from American shelves and introducing new tamper-resistant packaging. The episode inspired a true-crime show, “Cold Case: The Tylenol Murders,” released on Netflix this year.