Can Ultrasound Play a Role In Skincare NPD?

Sound propagates in elastic waves. Being “wavy,” sound has a wavelength, a frequency and a velocity. The wave, being elastic, can propagate in practically every medium except in the vacuum. It can also continue propagating when passing from one medium to another, as we learn when we apply our ears to a wooden door and listen to what is said in the neighboring room. Wavelength, frequency and velocity all depend on the propagation medium (sounds travel 350 m/sec in air and 1500 m/sec in water). 

When sound encounters an obstacle, part of it comes back as an “echo.” This phenomenon was observed in antiquity, and the ancient Greeks invented the myth of the loquacious nymph Echo (hence our word “echo”). Echo was one of Zeus’s mistresses and in revenge, Zeus’s wife Hera made her only able to speak the last words spoken to her. The pattern of the echo depends on the characteristics of the reflecting obstacle, such as its size and shape or the stiffness of the material from which it is made. Echography is the technology developed by studying the generation, the transmission and the reflection of elastic waves and their analysis.

Sounds and Ultrasounds

The time necessary for a vibrating particle in an elastic medium to go back and forth once, is called the period. The number of periods in one second is called frequency. Herz (Hz) is the unit of frequency (one Herz is one period per second). The human ear can detect sound with frequencies as low as 20 Hz and up to 20 thousand Herz (20 kHz). Sounds with frequencies above 20 kHz are called ultrasounds. 

Diagnostics

Ultrasounds are used in medicine as diagnostic tools; for instance, to perform the analysis of the status of a fetus during pregnancy, study heart physiology with echocardiograms, detect gallstones and kidney stones or study uterine fibroids and cancers.

Ultrasounds can also be used to explore the structure of the skin. An example of this can be found in reference 1 where echo-genic and non-echogenic zones are pointed out. 

Echo-provoking (echo-genic) skin zones appear “white” (they send back ultrasounds) and zones that do not send back an echo appear black. The effects of treatments can be monitored by sonography, and modifications in the size and structure of the skin can be detected. One can expect, for instance, to observe a thickening of the dermis upon treatments stimulating its water retention capability. One could also use sonography to follow the variation of dermal thickness versus age (if any) in a sufficiently large cohort of volunteers of different ages.

A Therapeutic Tool

When exposed to a sound wave, particles of a material will oscillate about a fixed point rather than move with the wave itself. As the energy within the sound wave is passed to the material, it can result in heat generation. 

Heat can be used to increase the temperature of anatomical zones that have been previously damaged. If the temperature of the damaged tissues is raised to 40-45°C, an excess of blood supplying that zone will result, in therapeutic effects. Temperatures in this range are also thought to help resolve chronic inflammatory states. Ultrasounds induce the degranulation of mast cells, causing the release of arachidonic acid, a precursor for the synthesis of the inflammatory mediators prostaglandins and leukotrienes. Thus, the overall influence of ultrasounds is pro-inflammatory, and the benefit of ultrasounds is not to “increase” the inflammatory response but to act as “inflammatory optimizers,” thus allowing the optimal inflammatory status to be obtained to prepare the tissue for proliferation and remodeling. Two other mechanisms are of interest for the therapeutic use of ultrasounds. One is the so-called cavitation or the formation of tiny bubbles that release a lot of energy when they collapse and can thus provoke the lysis of nearby cells. Incidentally, this is the reason why ultrasounds are used to break cells open as a first step to extract and purify cell components. The other is the so-called acoustic streaming which consists in the rapid circular movement of fluids around the cells. This phenomenon affects the diffusion of molecules and the permeability of membranes. For instance, upon treatment with
ultrasounds, the permeability to sodium ions is altered and this changes the cell membrane potential, and the transport of calcium ions across the membrane is modified, and this influences the mechanisms controlling many enzymatic reactions.

Skincare Applications

The skincare industry is eagerly searching for non-invasive, effective treatments to fight the signs of aging, such as wrinkles, sagging skin, fat mobilization (“double chins”) and roughness, and restore elasticity, tonus, and plumpness. 

Ultrasounds could disturb the orderly structure of the dermis and signal fibroblasts the need for new macromolecular synthesis. Ultrasounds could act as massaging tools and attenuate the effects of fat mobilization and the unwanted accumulation of fat on the jaw. Several studies have been performed and at least one comprehensive review of this topic has been published.² In the words of the authors: The literature study results revealed that significant improvements in the overall aesthetics of sagging of the mid and lower face could be accomplished by using a micro-focused ultrasonic treatment plan. Patients report no considerable side effects, and the results were also long-lasting. Ultrasound treatment can activate deeper tissues without causing injury to the epidermis, which sets it apart from all other skin-tightening methods. Better improvement rates have been reported by both patients’ self-assessments and clinical investigators’ evaluations.

If the results obtained with ultrasound treatment, in addition to being statistically significant are also relevant, perhaps ultrasound is one method to develop for efficient anti-aging treatments.

References

1. Levy, J., Barrett, D.L., Harris, N. et al. High-frequency ultrasound in clinical dermatology: a review. Ultrasound J 13, 24 (2021). https://doi.org/10.1186/s13089-021-00222-w
2. Khan U, Khalid N. A Systematic Review of the Clinical Efficacy of Micro-Focused Ultrasound Treatment for Skin Rejuvenation and Tightening. Cureus. 2021 Dec 4;13(12):e20163. doi: 10.7759/cureus.20163. PMID: 35003992; PMCID: PMC8722640.

Paolo Giacomoni, PhD

Insight Analysis Consulting

paologiac@gmail.com
516-769-6904

Paolo Giacomoni 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 .