Isaac Asimov wrote science fiction stories. He represented in the future, events that occurred in the past. He knew history and social sciences. When asked about the best secret weapon, he answered: the one that is not secret and that nobody notices. As an example, he quoted the long bow, which was able to shoot arrows 20 meters further than the cross bow. Thanks to the long bow, the archers of King Henry V, in spite of dysentery and exhaustion, won the battle of Agincourt against French troops equipped with cross bows.

In a same thinking frame, when somebody asks me about “my” secret ingredients, I answer that “my” ingredients are not secret, but nobody pays attention to them.

What is an “Active”?

Let us forget the FDA for a moment. As cosmetic scientists, our goal is to improve the skin—be it for its appearance or for its health. In both cases, the result is the consequence of the topical application of concoctions containing ingredients that are made of molecules which interact with molecules of the skin. A moisturizer, the most “neutral” of the concoctions, decreases dryness, reduces itch and increases suppleness and softness. It also allows the biochemical processes in the stratum corneum to be maintained, thus avoiding the penetration of foreign bodies that can provoke irritations and allergies. And the FDA (that I can’t forget) would like us to believe that all this is obtained via a non-physiological modification of the surface?

I remember how happy everybody was at L’Oréal when, after the introduction of the concept of exfoliation by Clinique, the newly-acquired brand Helena Rubinstein started formulating α-hydroxy acids and was granted the “right” to talk about “active cosmetics.” Exfoliation is obtained by a complex biochemical process that accelerates the natural process of the shedding of the outer layer of the stratum corneum. It provokes physiological and biochemical modifications that result, among other effects, in improved smoothness and luminosity to the skin. 

I hope we will soon be granted the “right” of talking about other cosmetic activities without being accused of being “drug dealers.” 

What Active for What Result?

Every topically applied concoction—be it called “neutral” or “active”—is endowed with biochemical activity. The action of the ideal skin care product is threefold: maintain, protect and repair. Maintain skin homeostasis, protect skin against damage-provoking environmental aggressions and remove serendipitously provoked damage. We speak here of damage generated at the molecular level: when damage is visible (wrinkles, age spots etc.), we need other actives such as tighteners or foundations to temporarily conceal the damage.

The best products to maintain skin homeostasis are the so-called moisturizers and exfoliators. I will not suggest to add one more ingredient to the panoply of humectants at hand. I would only like to recommend hyaluronic acid (HA) to be formulated with a pinch of an inhibitor of hyaluronidases, such as 0.1% apigenin or 5% chelatin, to avoid HA hydrolysis and prolong the moisturizing effect. Exfoliators are used in the eye zone and contain acids that can sting. Ascorbic acid (aka vitamin C) is a particularly welcome exfoliator because it also contributes to the maturation of ceramides in the cornified envelope thus promoting a well-differentiated epidermis. Activators of stratum corneum proteases such as Recoverine (Castanea sativa extract) achieve elegant exfoliation without stinging. In addition, Recoverine is synergistic with salicylic acid so that successful exfoliation can be achieved with less acid, as it was the case with Turnaround Concentrate that contained a pinch of Recoverine and 10 times less salicylic acid than the competitors. Exfoliators can also be conveniently used in anti-acne products to unclog pores and allow environmental oxygen to take care of locally niched anaerobic bacteria.

Protection of the skin is mainly afforded by the use of sun-filters and antioxidants. The choice of sun-filters is dictated by the legislator; antioxidants are chosen by the chemist or by the marketing executives. There is no need for antioxidants originating from exotic botanicals or oriental philosophies. One should use one antioxidant per reactive oxygen species: mannitol or ergothioneine for the hydroxyl radical, α-tocopherol for superoxide, bakuchiol for peroxynitrites; and astaxanthine, lycopene, acetyl zingerone or β-carotene to scavenge singlet oxygen, or Hall Star’s Micah [INCI name: Bis(Cyano butylacetate) anthracenediylidene] that inhibits its formation. α-tocopherol (aka vitamin E) has been shown to actively promote survival of cells exposed to UVA or UVB even when added several hours after the irradiation, and in the presence of vitamin E, UV does not provoke spongiosis, the phenomenon typical of human epidermis exposed to solar radiation.

Repair is the removal of damage. The most damaging environmental factor is solar UV. The primary target of solar UV is the DNA of epidermal cells. DNA damage has been causatively linked to the inflammatory response (erythema) triggered by UV radiation. After exposure to UV, one observes the inhibition of ATP synthesis and the impairment of the cutaneous immune response. The synthesis of ATP is inhibited because when nicotinamide adenosine dinucleotide (NAD) level is low, ATP synthesis cannot take place and, to repair damaged DNA, NAD is digested and polymerized as poly ADP-ribose. NAD levels are restored by topical application of nicotinamide, with the consequence that ATP synthesis and the immune response resume and that DNA repair is boosted. Nicotinamide, a.k.a. vitamin B3, is a must for skin care, the more so because it has been shown to inhibit the transfer melanosomes from melanocytes to keratinocytes, thus playing a possible role in evening out discolorations. After prolonged exposure to UV, one’s skin might need some soothing treatment. The gorgonian (sea whip) extract is better than hydrocortisone in treating and alleviating the pains of solar erythema.

When damage is visible, cosmetic “repair” can only be transient. Permanent “repair” can be obtained only surgically. Wrinkles can be made less visible by applying tighteners, such as proteins from an almond seed extract (Polylift) or from milk (lactofirm). When the tightener is applied together with an inhibitor of proteases such as 0.3% White birch extract, 0.1% ursolic acid or 0.2% hesperidin, the tightening effect’s duration is improved by up to a factor of two, from two-three hours up to five or six. When the tightener is a starch, the amylase inhibitor that can be used is 0.2% Boswellian.

Conclusion

As it was the case for the long bow in the warfare at the time of the Hundred Years War, not all the chemists or marketing executives pay attention to ingredients endowed with real, multiple biochemical activities and cosmetic efficacies. And not all the chemists or marketing executives consider taking advantage of activating or inhibiting stratum corneum enzymes to improve the results of their products. 

Let us hope that dermatologists attentive to cosmetic science will sound the clarion.

Paolo Giacomoni, PhD of Insight Analysis Consulting acts as an independent consultant to the skin care industry. He served as executive director of Research at Estée Lauder and was head of the department of biology with L’Oréal. He has built a record of achievements through research on DNA damage and metabolic impairment induced by UV radiation as well as on the positive effects of vitamins and antioxidants. He has authored more than 100 peer-reviewed publications and has more than 20 patents. He is presently head of R&D with L.RAPHAEL—The science of beauty—Geneva, Switzerland. His email is: [email protected].