Let's talk science: Growth factors are signaling molecules, usually large proteins. Cosmetic dermatologist, chief medical officer and founder of PFRANKMD, Dr. Paul Jarrod Frank, says that there are innumerous types throughout the body and many found naturally in skin.

Dermatologist Dr. Hadley King further explains that EGFs communicate messages relevant to growth and healing to the cells in skin. "When these signaling proteins bind to receptors on cell surfaces, they can send instructions to replicate, repair and rejuvenate," says King. "These messages can stimulate keratinocytes, melanocytes and fibroblasts, which produce collagen and elastin to thicken and tighten the skin."

Here's the thing, though: As we age, our skin produces smaller quantities of these growth factors... which is exactly where EGF skin care products come in.

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Wondering how these incredible growth-stimulating proteins are transferred to a moisturizer or serum? Frank says that there are skin-derived options from a human source or bioengineered EGF products, sometimes from trick plant cells. Celebrity facialist and founder of Joanna Vargas Salons and Skin Care, Joanna Vargas, says that the peptides or protein chains are developed specifically to speed up wound healing at a cellular level.

"We have EGF in our skin to help repair and replicate existing cells," says Vargas. "EGF in skin care is meant to stimulate the same type of function in order to rejuvenate the skin and increase collagen production."

Growth factors are often found in serums and masks, but they are also in face and eye creams.

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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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