No. 3 Hair Perfector.

"Olaplex's Number 3 Hair Perfector contained this ingredient, which was obviously a big problem as the hair perfector was a bestseller for the brand, so the idea that it might cause fertility issues was incredibly damaging to the brand's image. Olaplex CEO Ju Wong released a statement saying that lilial was only used in their hair perfector for fragrance purposes at a concentration of 0.0119% and that it wasn't an active or functional ingredient, whereas the ingredient was given to rats in ridiculously large amounts which weren't realistic in the real world. She also pointed out that the study had rats ingest lilial whereas that isn't what humans do, you don't eat your shampoo, you rinse it off."

"Olaplex No. 3, which is the one that a lot of people say you should be using because it's the most potent, was never designed as the conditioning treatment that everybody's treating it like. They're assuming that Olaplex is a conditioning treatment that will make hair softer and more manageable, but it's only really meant to change the structure of the hair without any sort of coating. You're not supposed to drench your hair in it, put it in a bun, put it in a hat, then sleep with it. I used to work in a salon and Olaplex was a huge part of our bleaching treatments. Depending on the hair type, we'd be like, we're not going to do your hair unless you allow us to use Olaplex, because it can snap, it can break. It was a system, it was part of a process. When people started using No. 3 on their hair when they didn't even have color in their hair or anything like that, I was confused. Treating it like a leave-in conditioner, I don't think that's really how it goes."