As soon as Kylie Jenner made the announcement, she began selling Kylie Skin, a new line of skincare products. Given the phenomenal success of her Kylie Cosmetics brand, the one that made her a billionaire, this seems like a pretty logical move.

But there was some internet controversy. The initial collection’s walnut face scrub is at the center of controversy; other products in the line-up include a foaming face wash, vanilla milk toner, face moisturizer, vitamin C serum, and eye cream. According to a tweet from Kylie Skin, the scrub contains “fine walnut powder,” which is where the issues started.

So what specifically may go wrong with this kind of face scrub? According to New York dermatologist Joshua Zeichner, M.D., “Walnut shell powders have long been used in face washes but have gone out of favor because of allegations that they create microscopic tears to the outer skin layer.” He says, “It’s unclear if this new scrub comprises walnut shell or the walnut itself, but it does contain walnut powder. “Furthermore, it’s not clear if the walnut powder is the same as earlier formulations or how finely it was produced. Depending on how it is created, the same component may function quite differently in terms of both effectiveness and safety.”

A class action lawsuit was filed in 2017 as a result of similarities between the product and the St. Ives Apricot Scrub. One of the main plaintiff claims in the lawsuit was that the crushed walnut powder causes microscopic skin tears, which exposes the skin to infections and discomfort. However, it should be noted that the lawsuit was finally dismissed in December 2018 when the judge determined the claimed charges lacked supporting evidence