Cosmetic surgeons know well the fine line that exists between marketing spin and what has been scientifically proven to work. The same goes for cosmetic skin care: While there is no shortage of products promising to diminish signs of skin aging, only a few ingredients have actual science to back their claims, experts say.

MAKING THE CUT

Dermatologists agree the gold standard is the retinoid — first and foremost, prescription tretinoin. Over-the-counter retinoid derivatives include retinaldehyde and retinol.

Retinoids are the tried and true molecules that not only help increase collagen production, but also enhance cell turnover, normalization of the stratum corneum, remove pigment in the skin, normalize epidermal cells and make pores smaller, according to Kathy Fields, M.D., dermatologist and assistant clinical professor at University of California, San Francisco's department of dermatology.

"That is square one," Dr. Fields says.

IN THE WORKS

Peptides, growth factors, botanicals and even stem cells are making headlines in skin care.

"This would be...inclusive of all aspects including stem cells (adult and embryonic); growth factors; engineered proteins (proteonomics); recombinant DNA products to fight/halt/reverse aging; the next wave of human growth hormone, or HGH; and a better understanding and control of immune system function, along with the relative and absolute declines in hormonal balances," Dr. Werschler says. While some of these mechanisms of action might pan out, others might not.

The latest news in stem cell technology, according to Dr. Fields, is in retrieving the cells from plants.

"[The theory is that] you get all the ingredients to create new life from a cell ... such as growing skin," she says.

"Peptide technology...works on so many levels. Peptides can be anticancer, antimicrobial, antibacterial, stimulate collagen, stimulate growth factor," she says.

But dermatologists also question the viability of some active ingredients.

"...growth factors on the market, which are huge molecules that are very unlikely to penetrate the skin, ...would make terrific moisturizers," Dr. Spencer says. "We have penta-peptides and hexa-peptides [but again] penetration is the issue. I do not mean to be too skeptical but...you put these molecules on the outside of the skin and they have to get in to work. That does not mean that they do not work, it is just that they have not been shown to work."