When I read that New York City-based celebrity facialist Georgia Louise gave Sandra Bullock and Cate Blanchett a “penis facial”—and that it costs $650 per treatment—I did not flinch. I didn’t even flinch when I read further that the serum used for the treatment is made from stem cells derived from the removed foreskins of newborn babies in South Korea.

It might seem extreme. But you can actually find the same protein Louise uses in her penis facial— epidermal growth factor (EGF)—in a variety of skincare products, including the ones on your bathroom counter right now. I use them. Even Oprah endorsed a cream with foreskin-related compounds in them.

If baby foreskins make you nervous, take note: the science here is a bit more complicated. Rita Levi-Montalcini and Stanley Cohen’s discovery of EGF earned them Nobel Prize in 1986. EGF has been shown to promote wound healing in clinical studies. And this is where the foreskins come in. EGF is derived from human tissues, including skin, kidneys, and male genitalia (in some cases, foreskins). It can stimulate cell proliferation, and a 2016 clinical study found that twice-daily applications of EGF serum for three months can significantly improve “brown spotting, skin texture, pore size, red spotting, and wrinkles versus baseline.” (Although that study was funded by the manufacturer of the product tested.)

You can find EGF in a variety of skincare products: DHC EGF Cream, Mizon Bee Venom Calming Fresh Cream, DNARenewal Regeneration Serum, Bioeffect EGF Serum, and Peter Thomas Roth FIRMx Growth Factor Extreme Neuropeptide Serum.

EGFs are just one of several beauty products rooted in foreskins. The SkinMedica cream beloved by Oprah, for example, contains “human fibroblast conditioned media,” which are essentially stem cells that have been grown in a lab, but which the company says were cultivated originally from the stem cells of a single baby foreskin 20 years ago.

Foreskin-derived lotions and potions—which certainly different—actually have some serious competition for the most unusual beauty products on the market. Urine, in the form of urea, is a common ingredient. Former orthopedic surgeon Barbara Sturm makes a custom cream reportedly derived from your blood after it’s been stimulated to mimic its healing process after injury. (She is also a pioneer of the vampire facial, which similarly uses cell platelets to stimulate cell turnover.)

Perfume, meanwhile, has traditionally contained ambergris, made in the digestive system of blue whales, and musk, secretions from the anal glands of animals like the musk deer and muskrat. Cochineal beetles have long been crushed up for their red pigment for lipsticks. Fish scales are used for their iridescent quality for shimmer-based cosmetics. Snail secretion is ubiquitous in k-beauty products. Or you might not care about the specific ingredients in your products, though, as long as they work.

“I am always very mindful to explain radical serums and potions that I carry in my back bar so I always explain that EGF is derived from newborn baby foreskin, from which cells were taken and then cloned in a laboratory,” Louise told People. “I remember the time when I used placenta from a pig on a client that was vegan and that didn’t end so well.”