King says that plant versions are bioengineered in a lab and can be barely-grown EGFs, such as those found in Bioeffect and DNAEGF Renewal. Vargas sources EGF from fruits and vegetables for her product line.

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Hadley says that the human stem cells can come from any source. And we mean any source. In fact, this is where the "penis facial" got its nickname: Georgia Louise's Hollywood EGF facial reportedly uses EGF derived from cells from the removed foreskin of newborn Korean babies (yes, really).

SkinMedica also uses epidermal growth factors in its products. They're derived from several different human cells grown in a laboratory, including skin cells, bone marrow stem cells and fat stem cells. The growth factors can even be extracted from a person's blood, or platelet rich plasma (PRP).

King says that the SkinMedica TNS Recovery Complex, $179, specifically contains proteins derived from the fibroblasts of neonatal foreskin.

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King says that growth factors have been of particular interest for topical products because of their ability to promote wound and ulcer healing when applied topically. One study highlighted how a serum containing recombinant EGF showed significant improvement to brown spots, skin texture, pore size, red spots and wrinkles, when applied twice daily over a three-month period. (Schouest JM, Liu TK, May RL. J Drugs Dermatol. 2012; 11(5): 613-620.)

Their wound-healing ability makes EGF products perfect after laser treatments, according to Vargas. The laser is meant to stimulate collagen production. This collagen boost combined with wound-healing EGF has a transformative effect. Similarly, Vargas adds that growth factors are helpful for repairing sun damage and skin mutations from environmental stress.

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The experts agree that growth factors are suitable for all skin types, although King explains they are targeted for aging skin.

Frank adds that EGFs don't cause sun sensitivity. (Of course, that's not a free pass to skip sunscreen!) Also, unlike some ingredients, Frank says that growth factors can be used in conjunction with other antioxidant or retinoid products to improve skin quality, thickness and health.

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EGF is one of the newer ingredients in skin care which means that it hasn't been as extensively researched as others. "They are less data-proven compared to sun protection, retinoids, alpha hydroxy acids and antioxidants," says King. "But there is definitely potential. And they are less irritating compared to retinoids and alpha hydroxy acids."

Frank continues that there are some studies, but growth factors are not considered as potent as some other anti-aging superstars, like retinoids. "There are some that question their effect at all given that the molecules are considered too large to penetrate deep into skin," says Frank. He also notes that the main concern is that growth factors could speed up production of skin cancer, but "it is unproven."

Take note: Vargas says that EGF has had a lot of very misleading and irresponsible marketing over the last few years. However, that doesn't discount the ingredient's performance. "It's highly effective and very exciting to me," she says.

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