To be effective, a skin care treatment has to deliver either actives in a formulation, an applied therapeutic energy, or both. Not only that, but these need to be to a depth where it will stimulate a change that results in a visible improvement the skin. But how deep should that be? In a recent television ad one company proclaimed, with a simple image, that the moisturizing effect of its product could travel down through multiple cellular layers to have a long-lasting hydration effect. However, the ad was also very careful to display the words "stratum corneum" in small print, just in case regulators jumped on them thinking the company was claiming delivery as deep as the viable epidermis or perhaps even the dermis.
But how deep should such a stimulant (e.g. light, ultrasound, ascorbic acid, retinoids, etc) travel to really end up having a visibly efficacious effect? To trigger collagen expression, for example, one needs to transport this stimulant as far down as the papillary dermis (<1mm) to cause expression of collagen from fibroblast cells. Alternatively, a stimulant may only need to be delivered as far as the dermal-epidermal junction to stimulate expression of the elastic protein fibrillin-1 in this region. In each example, an increase in these proteins is known to reverse the progressive atrophy and loss of elasticity in aging skin.
Techniques to elicit this response don’t have to be an active substance but could be an energy type, such as light, in the near infra-red or high frequency (e.g. 3-5MHz) ultrasound, both of which are known to boost collagen concentration through localized heating. If used with an active substance, and providing the molecular weight isn’t too high (ideally<500), these energy types can also be used to enhance delivery or trigger release of an active in situ. Such actives could be small peptides or encapsulated unstable actives such as vitamin C. But if these are to be sold as cosmetic treatments then they must be considered by regulators to be "articles intended to be rubbed, poured, sprinkled, or sprayed on, introduced into, or otherwise applied to the human body...for cleansing, beautifying, promoting attractiveness, or altering the appearance."
This FDA cosmetic definition therefore does not allow for deep delivery or physiological outcomes such as increasing protein content, vascularity or cellular proliferation; all of which are positive effects that reverse the symptoms of aging skin. There is also a less defined rule that if an active is claimed to be delivered any deeper than the (unviable) stratum corneum, it needs to meet extremely rigid safety/toxicity regulations, especially if it then has a known physiological effect, as it then becomes drug.
So what’s the answer? Often cosmetic skin care companies deliberately utilize chemical penetration enhancers to have a deeper physiological effect than necessary to achieve the visible changes needed, in order to sell more product. However, they will not be able to claim such blatant depth of delivery or structural and functional changes for fear of reprisals from the regulators and advertising standards agencies, especially if there isn’t clinical and safety data to back up these claims. This is the same for cosmetic devices that apply some kind of energy to get a visible effect, as they will meet the same challenge of wanting to make physiological claims to appeal to consumers. Alternatively they may choose to claim these more medical changes by securing medical device recognition such as FDA 510k approval; a process that will incur extra expense in demonstrating clinical efficacy and safety but could ultimately be worth the extra effort.
The cosmetic skin care world is really not a million miles away from the transdermal drug delivery one. Both need to overcome the formidable barrier of the stratum corneum to deliver actives to at least the depth of dermal-epidermal junction to have any efficacy. Unless a localized drug effect is required, the drug delivery company typically needs to deliver enough of the active to the upper papillary dermis where diffusion into capillaries results in systemic transport and benefits from avoiding hepatic first pass metabolism. The cosmetic skin care company, on the other hand, also needs to deliver the actives to at least this depth but requires the active to have longer residence time to have the local effect needed (e.g. anti-ageing), ideally without being carried off by the microvasculature before it has time to act.
Therefore, for cosmetic companies wishing to remain as such, their products should deliver the active deep enough to achieve efficacy but should avoid delivery depth claims and structural or functional claims even if the product needs to do that to achieve visible efficacy. Cosmetic companies continually press against the boundaries of the cosmetic definition to claim one-upmanship efficacy of their products and time and time again we see regulators such as the FDA object to this and demand its removal from advertising. There’s no easy answer, either be careful of claims or go the whole hog and get medical device, drug or device/drug combination approval and make the scientific claims you want to make.
About the Author Dr. Peter Luebcke is a specialist senior technology consultant at Sagentia in the field of consumer products with particular focus in the personal care sector. He has first-hand experience leading a personal care products startup and was intimately involved in both the design and development of products that fall into the blurred interface of consumer products and medical devices. He also has extensive biomaterials, engineering R&D project management and technology commercialization experience. Sagentia is a global innovation, technology and product development company that provides outsourced R&D consulting to start-ups through to global market leaders in the medical, industrial and consumer sectors.
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