Dermatology has been traditionally classified as a medical specialty; however, this perception is rapidly changing. While dermatologists use creams and pills to treat skin disease, they have also pioneered novel surgical techniques. For example, the concept of tumescent anesthesia was developed by dermatologists Jeffrey Klein, MD, and Patrick Lillis, MD. This method for performing outpatient surgery and liposuction anesthetizes the body and not the brain. The undesirable side effects associated with general anesthesia, such as nausea, fatigue, postoperative pain, and emotional labiality, are not experienced with the tumescent technique. Now, dermatology is tackling the next frontier in medicine, which is the use of physical modalities. These physical modalities include the use of light, current, heat, and vibration to modify skin function.
Physical modalities are the basis for the new dermatologic devices. These devices are found in both the professional and home arena. Dermatologists are familiar with the lasers used for skin rejuvenation and hair removal, but these same devices are now being adapted for home use. The home device arena will be the next new explosion in skin care, with dermatologists again leading the way.
The home skin care devices can be classified into several categories: resistive heating, motorized, galvanic current, blue light, and red light. Each of these technologies potentially offers a different skin benefit to the consumer. This editorial evaluates the home device arena.
Some of the first devices to capture the attention of the consumer for the treatment of medical disease were based on resistive heating. These devices used a battery to generate electricity that was converted into heat via resistive loss and applied to the skin through a localized probe inducing vasodilation. This device was used to speed the resolution of acne lesions. The heating devices led the way to the development of mechanized facial cleansing. The cleansing devices combined a brush with rotary, vibrating and sonicating motors to provide better skin hygiene. The mechanized cleansing devices not only removed sebum and cosmetics, but also provided skin exfoliation. This concept of better appearing and better functioning skin encouraged consumers to look to home machines as a supplement to skin cleansers and creams.
The next home device revolution occurred when spa equipment was introduced to the consumer. Galvanic current had been used by estheticians for years to supplement the application of facial creams. Low-voltage current was thought to change the permeability of the skin. The adaptation of galvanic current machines to a hand-held home unit allowed the consumer to apply a moisturizer to the face followed by the application of galvanic current. Indeed, I have been able to demonstrate enhanced water content of the skin through corneometry when an occlusive moisturizer was massaged into the face with galvanic current. Thus, home galvanic devices combined traditional medical skin care with a physical modality.
The latest innovation in home devices has been the introduction of concentrated light, including green, yellow, red, and blue. Each of these wavelengths of light is used to produce a different skin effect. Green, yellow and red diodes were the first light devices introduced. The repetitive flashing of the various diodes in a predetermined pattern was thought to induce a downregulation of MMPs, thus decreasing collagen degradation. In order for low-power visible light to have an effect on the skin, the photons must be absorbed by a chromophore or photoacceptor. The cellular photoacceptor signals a pathway that is upregulated or downregulated by light. This is possible because each skin structure has certain optical properties characterized as the “optical window.” For example, skin tissue absorbs better in the blue spectrum than in the red spectrum. Hemoglobin and melanin absorb at wavelengths shorter than 600 nm, while water absorbs at wavelengths greater than 1150 nm.
The two wavelengths of light that have found the most biologic use in dermatology are blue and red. Blue light was originally introduced to the dermatologist for the in-office treatment of acne with or without a photoinducing agent. Blue light excites porphyrins on the skin produced by proprionibacterium acnes, thus physically killing the organism responsible for acne lesions. The safety and ease with which blue light can be applied to the skin has given rise to home devices for acne treatment. Several of these devices have been or are being approved by the FDA through the 510K approval route. Home-use devices are smaller and less powerful than professional devices, thus the treatment time is increased, but this shortcoming may be balanced by the ease of home application.
Finally, red light has been studied for its utility in skin rejuvenation. Light in the red and near-infrared range (600–950 nm) has the greatest skin penetration and thus represents the wavelength with the greatest potential for modifying skin function. The theory behind the effect of red light on the skin is based on the absorption of monochromatic visible and near-infrared radiation by the cellular respiratory chain. Cellular respiration occurs in the inner mitochondrial membrane which contains five complexes. Complex I is NADH dehydrogenase, complex II is succinate dehydrogenase, complex III is cytochrome c reductase, complex IV is cytochrome c oxidase and complex V is ATP synthase. Complex IV or cytochrome c oxidase appears to be the primary photoacceptor for red and near-infrared radiation in mammalian cells.
When cells absorb photons of red and near-infrared radiation, electronically excited states are induced leading to the acceleration of electron transfer reactions in the mitochondria. The increase in electron transfer enhances the production of ATP, which speeds cellular metabolism. As ATP is the substrate for adenyl cyclase, increased ATP also increases cAMP. Thus, red light devices may increase cellular metabolism, which increases the synthesis and secretion of various proteins in turn enhancing skin function. This is the basis for the red light devices that are now sold for skin rejuvenation in the home market.
The area of consumer dermatologic devices is in its infancy. There can be no doubt that the combination of topical agents with devices presents new opportunities for the enhancement of skin function. Heat, light, and vibration are safe modalities that may influence the skin in ways that are not currently understood. It is the accessibility of the skin, the largest body organ, which even makes device application possible. New research by dermatologists in this area provides even greater diversity to the dermatologic armamentarium.