LEEDS, England—At a testing center here, for three days in a row 10 women at a time line up with their arms raised over their heads.
A technician wearing a face mask and gloves sprays them with antiperspirant for precisely two seconds.
The women then return to the center after 72 hours for what Unilever calls “torture testing.” They sit in a room with the heat set at 104 Fahrenheit and a humidity level of 40% for an hour so Unilever employees can collect their sweat. At another site 90 miles west, odor assessors sniff the underarms of people in a separate testing group to rank the intensity of smells Unilever refers to as “meaty” or “cheesy.”
For more than a decade, Unilever, the world’s largest maker of deodorants and antiperspirants, has been conducting tests like these to develop its strongest antiperspirant technology yet.
The project, code-named Invictus, involved 60 scientists, 50 formulations and more than 200 clinical studies, leading to what Unilever says is the largest change to its antiperspirants in three decades. The company has been rolling out antiperspirants that promise to keep underarms dry and odor-free for three days under its Dove, Degree, Rexona and other brands.
The 72-hour-protection claim, while rooted in science, is essentially a marketing tactic used on and off by companies to sell deodorants and other consumer products for years. Unilever’s new technology has emboldened the London-based company to double down on the claim by promising three days of nonstop protection and going head-to-head with rivals like Procter & Gamble.
“If you rationalize it…you go ‘oh goodness me I shower I don’t need that,’” said Kathryn Swallow, head of Unilever’s deodorants business. “But at that point of purchase where you’re looking for something in a nanosecond, they are a quick-fire navigation tool.”
Of the millions of sweat glands across the human body, it’s the ones under the arms that trap sweat, which can create odors. While deodorants seek to mask these, antiperspirants aim to stop sweat, typically using aluminum salts that dissolve in the moisture to form a gel. The aluminum in the antiperspirant essentially forms a plug that stops sweat from escaping.
Developing new technology isn’t easy, partly because the opening of a sweat gland is smaller than a pinhole, making it hard to look inside. Until Invictus, Unilever had relied on a technology it patented in the 1980s. Subsequent efforts to find something more advanced had stalled.
The “lightbulb moment” came in 2011 when one of Unilever’s scientists discovered that a combination of calcium and glycine could manipulate aluminum molecules to form a stronger barrier to stop sweat seeping through, says Alan Palmer, R&D head for Unilever’s personal-care business.
After years of subsequent testing and refining, the company launched the first product using its new technology in 2018 for Rexona in Australia. It began selling Degree Advanced in the U.S. last year and Dove Advanced Care in the U.K. this year. Demand for products using its new technology helped boost deodorant sales in Europe and Latin America during the third quarter, the company recently said.
Unilever’s testing center in northern England—a low-slung redbrick building adjacent to a thrumming factory that churns out 700 million sprays, sticks and roll-ons a year—is one of two sites that conduct all of the company’s antiperspirant and deodorant testing globally. People around the world sweat similarly, Unilever says.
The company tests all products on women, saying they tend to be more available during the day than men. To participate in its paid study, women must pass a physical fitness test, produce 100 milligrams of sweat and avoid antiperspirants for 17 days prior. Violators are caught out by a swab test taken on the first day.
For the first 40 minutes in the hot room, the women warm up by sitting largely still on towel-covered chairs—although they’re allowed to flip through magazines provided, like Women’s Weekly and OK!—and make gentle conversation.
“Some of them are friends and see this as a bit of a social occasion,” says Catrin Chan, who manages the process. “We try to make sure they don’t get overexcited.”
After a quick wipe with a tissue, a member of Chan’s team places a gauze under each woman’s armpit to collect sweat and leaves it for 20 minutes before removing and weighing it.
In an adjoining room, another group of women whom Unilever calls “sensory panelists” enter individual booths and strip down to their bras to apply stick antiperspirant—using six strokes per underarm—to evaluate how it feels.
These women have undergone four to six months of training so they can assess sticks but also sprays and roll-ons for factors like glide, wetness, coldness, stickiness, thickness and smoothness, and record scores on a 100-point scale. They also test whether the product will rub off on clothing by holding a black cloth against their underarms for a few seconds.
Despite the technological advances in deodorants, when it comes to testing Unilever says there’s no substitute for human sweat or sense of smell. “You can’t simulate the physiology of human sweat in a dead man or an instrument,” says Vivek Sirohi, head of R&D for deodorants.
The company has separately trained a group of eight odor assessors—men and women—to arrive at a “mean malodor score” by asking them to sniff “sweat pens” that look like whiteboard markers but smell like human sweat at varying intensities.
Once trained, assessors graduate to sniffing the underarms of real people. Subjects go about their usual day but must wear a standard T-shirt provided by the company and agree not to swim or eat spicy food beforehand. “The assessors can tell if somebody cheated and had a curry,” Chan says.
Unilever commissions real-world head-to-head tests of its antiperspirants against those of its rivals. It asks people to cycle, or run on treadmills or up and down stairs before collecting their sweat, and classifies sweaters using labels like “heavy” or “anxious.”
A recent TV ad pits Degree against Old Spice, made by Unilever rival Procter & Gamble. A man performs pull-ups and lifts his arms to show a sweat patch on his T-shirt where he used Old Spice and none where he used Degree. “Degree Advanced. Keeps Working When Others Stop,” says the voice-over. P&G, which makes its own 72-hour claim for Old Spice, declined to comment.
Unilever is also using the 72-hour claim to charge more for its products. A stick of 72-hour Degree costs $5.23 on Walmart.com, compared with $3.18 for the brand’s 48-hour protection line.
By pushing upscale and offering more benefits, the London-based consumer-goods giant hopes that it can better compete in the U.S., where it has been losing market share to deodorants such as P&G’s Native, which sells stick deodorants at $13. Another rival is Lume, whose $19 tube of deodorant cream also claims to protect against odors for 72 hours and is marketed as suitable for the entire body.
Advances in molecular modeling and quantum computing are allowing scientists to see better inside sweat glands and understand how aluminum molecules interact with them. Palmer says this gives him confidence that another big breakthrough is only five to seven years away. “There’s a holy grail out there called unequivocal guaranteed wetness control no matter what you do, where you are all day,” he says. “That’s the holy grail I’ll keep hunting for.”
Write to Saabira Chaudhuri at Saabira.Chaudhuri@wsj.com