By THÉRÈSE MARGOLIS    

You see it listed on a slew of skincare products, from night creams to facial masks, face cleansers to serums.

And dermatologists and beauty experts swear by it, touting it as God’s gift to aging skin, a multitask cure-all for everything from wrinkles and sagging skin to age spots and acne.

But for all the spiel about the benefits of glycolic acid, most women draw a blank when asked what exactly it is or how it works its magic to repair damaged skin.

“Glycolic acid is a member of the alpha-hydroxy acid (AHA) family, along with malic, citric and lactic acids,” explained derma-oncologist Ingrid López Gehrke during a presentation of SkinCeuticals latest anti-aging treatment, Glycolic 10 Renew Overnight.

“It is usually derived from sugar cane, and like other alpha-hydroxy acids, it helps to exfoliate and slough away the cells on the top layer of the skin, thus speeding up the skin renewal process.”

Cells on the superficial or upper layer of skin, known as the epidermis, are constantly replacing themselves, but as we age, this renewal process begins to slow and, as a consequence, skin can begin to lose its natural glow and fresh appearance.

Exfoliates, such as alpha-hydroxys, gently remove the upper surface cells to reveal a softer, younger-looking complexion that lies below.

“The use of alpha-hydroxys are nothing new,” López Gehrke said.

“Women have been using them for ages. Back in ancient Egypt, Cleopatra was known to take long baths in milk (rich in lactic acid) to keep her skin beautiful.”

The widespread use of alpha-hydroxys became popular in the early 1990s, when women around the world discovered that the fruit-based chemicals could significantly improve their skin appearance and texture, dramatically reducing the appearance of fine lines and wrinkles.

Cosmetic companies everywhere were quick to jump on the AHA bandwagon, and the beauty industry was suddenly inundated a plethora of fountain-of-youth products that promised to reverse the early signs of aging.

But while alpha-hydroxys were all the rage at the time, some scientists were beginning to worry that the unregulated use of AHAs could irritate delicate skin and increase sun sensitivity, potentially increasing the risk of skin cancer.

“The truth is that not all alpha-hydroxys are created equally,” López Gehrke said.

As it turns out, glycolic acid has two unique qualities that make it the gold standard for AHAs.

Glycolic acid is less aggressive than some other AHAs, López Gehrke said, which means that it is less likely to irritate skin or cause redness.

But more importantly, glycolic acid has the benefit of being composed of smaller molecules than other AHAs so it can penetrate deeper into the skin to the dermis and subcutaneous tissue, where it can work on the source of hyperpigmentation from sun damage.

Glycolic acid is also the most researched AHA and has the best track record for results in patients of all ages and skin types.

Moreover, glycolic acid has a natural ability to hydrate skin and can actually boost its ability to retain its own natural moisture, as well as stimulate collagen production in the dermis.

“But it is not enough just to apply glycolic acid or any other AHA to the surface of your skin,” López Gehrke said.

“You have to have your skin properly primed so that it can absorb the glycolic acid.”

To do this, she said, you need to first wash your skin with a soap or cleanser that has an acidic pH.

“Your skin is naturally acidic, so if you cleanse it with a product that is alkaline, you can irritate it, and it will not be receptive to whatever products you apply afterwards, including glycolic acids,” she said.

López Gehrke said that in order to penetrate into the dermis and below, a product such as SkinCeuticals Glycolic 10 Renew Overnight, which can only be purchased through a dermatologist or plastic surgeon, starts off with a higher percent of glycolic acid because not all of it makes it through the hyperdermis.

“The actual potency of Glycolic 10 is 14.6 percent, but by the time it reaches the dermis, it is only 10 percent,” she explained.

“And that is the right potency for achieving the results of a more even skin tone through the reduction of hyperpigmentation.”

López Gehrke said that SkinCeuticals Glycolic 10 is able to work on all levels of the skin to produce a more noticeable and immediate improvement of skin’s appearance.

“There are products with higher percentages of glycolic acid, some as high as 70 percent, but they are used exclusively by dermatologists and other specialists for peelings and similar in-clinic treatments,” she said.

“But Glycolic 10 is a product that, once approved by your dermatologist, can be used nightly at home to promote and maintain healthier, younger-looking skin.”

Like any chemical treatment, glycolic acid is not right for everyone.

People with ultra-sensitive skin or certain medical conditions and those who do not apply sunscreen religiously should probably steer clear of AHAs in general, and they are not advised for women who are pregnant.