I cried in the Uber on the way home, thinking, my curls are ruined. After a silk press gone wrong in 2022—too many passes of the flatiron, enough to see steam rising—I was left with heat-damaged hair that looked limp and lifeless. Before cutting it all off, I turned to Olaplex. I’d never used the brand, but I’d heard it could revive damaged hair. After a few washes with the No.3 Hair Perfector and the brand’s shampoo and conditioner, my curls started to bounce back. I still trimmed the dead ends (sadly, they were too far gone), but since then, Olaplex has been a staple in my routine.
In the years that followed, the brand expanded its bond-building lineup into curl territory, including a salon-exclusive treatment that left my curls ultra-bouncy, and a defining gel that’s powered more than a few twist-outs. The technology behind it all is what Olaplex is known for: repairing disulfide bonds in the hair fiber to strengthen strands from within. Now the brand is expanding its curl line to include the new No.4 Hydrating Curl Shampoo and No.5 Hydrating Curl Conditioner. I put them to the test—alongside three other Allure staffers with different curl patterns, from loose waves to tight coils—to see how the products stack up against the brand’s original shampoo and conditioner and other bond-building washday duos for curls.
Before we get into our reviews, however, it’s worth setting the stage for what these new products are and what they’re promising.
How do the New Olaplex Curl Shampoo and Conditioner Work?
Olaplex No.4 Hydrating Curl Shampoo
The original Olaplex shampoo and conditioner are designed to strengthen strands (thanks to the brand’s signature bond-building technology) while preventing frizz and gently cleansing the hair.
According to a press release from the company, the Olaplex No.4 Hydrating Curl Shampoo and No.5 Hydrating Curl Conditioner do all of the above, but with added benefits for curls. This includes providing “a more defined curl pattern in one use and, over time, seven days of hydration, 50% less frizz, even in high humidity, and easier detangling.”
Before offering insight into the new formulas, cosmetic chemist Lily Njoroge shares this disclaimer: “An ingredient list can give us a strong sense of how a formula should theoretically perform, but ingredient concentrations and how they interact with each other ultimately determine whether a product delivers on its claims.”
Keeping that in mind, Njoroge explains that the formula leans heavily on moisture-retaining ingredients: hydroxypropyltrimonium hyaluronate, a modified, positively charged form of hyaluronic acid, and glycerin to support both hydration and strand manageability. “Hydroxypropyl bis-hydroxyethyldimonium chloride [in the formula] attracts and binds water while also providing a protective layer that helps the hair retain moisture even in changing humidity,” she explains.
The shampoo is also boosted with time-released emollients like avocado oil and sunflower seed wax to soften and hydrate strands, which can make detangling easier.
As for curl definition, the formula achieves that with polymers—acrylamidopropyltrimonium chloride/acrylamide copolymer, polyquaternium-11, and polyglycerin-3—that “help define and hold curl shape while improving elasticity,” says Njoroge, though results can vary depending on factors like curl pattern, porosity, and water quality.
Njoroge points out that the shampoo also includes ingredients that support the Olaplex frizz-reducing claims. “Polyquaternium-7 works alongside polyquaternium-11, hydroxypropyltrimonium hyaluronate, and acrylates copolymer, helping to form humidity-resistant barriers,” she says. This barrier keeps moisture from getting past the cuticle, which keeps stands smooth and frizz-free.
Olaplex No.5 Hydrating Curl Conditioner
The conditioner shares many of the same ingredients and claims as the shampoo, but the feel is noticeably different. “That’s largely because of how the conditioner base is built,” says Njoroge. She points to behentrimonium methosulfate (one of her favorite conditioning agents), which “coats the hair shaft to reduce friction and static without causing buildup, while delivering the slip that makes detangling easier, especially for curly and coily hair, where friction can lead to breakage,” says Njoroge.
