Skin Deep

Defining skin quality and how to assess it

Skin quality has long been an indicator of health and desirability. Whether consciously or subconsciously, rightfully or wrongly, judgment of a person’s health, vitality and youthfulness is often passed based on a quick assessment of their skin including smoothness, tone, and elasticity. Going deeper, age and race as divulged by a person’s skin has led to reasonings of love, hate, prejudice, social ostracization, financial gains or losses, and even world wars. It is no surprise then, that the medical aesthetics field is experiencing a boom, with more and more people seeking to maintain or improve that facet essential to their social well-being. Cohesion and specificity around the terminology describing skin quality is surprisingly lacking in clarity, which is an essential component in properly addressing what we are seeking to correct and how to best go about it. Below is a review of a few studies that attempt to establish a guiding framework for terminology used in assessing skin quality, and how that informs treatment, especially with injectables such as neurotoxins and fillers.

Categorical Definition

Psychologist Nancy Etcoff is credited with saying that beauty is intuitive, but the definition of beauty is subjective, mutable, and difficult to articulate with words. Currently, the literature around skin quality focuses largely around age-related changes, but  standard, clear and comprehensive definition and evaluation tools for quality should exist beyond the parameters of age. In an attempt to create such a framework, Drs. Shannon Humphrey, Stephanie Brown, Sarah Cross, and Rahul Mehta defined skin quality within three fundamental categories: visible, mechanical, and topographical (Humphrey et al., 2021). Visible attributes include things such as redness, dullness, sallowness, radiance and pigmentation. Topographical characteristics include roughness, dryness, lines, and hydration, while mechanical aspects include elasticity, pliability, firmness and thickness. As can be deduced, some attributes can overlap categories – most topographical qualities are also visible and/or mechanical. Some attributes, such as scar, fall within all three categories. See Table 1 for a useful list for skin quality attributes and their proposed definitions. 

A different study attempting a similar definition, titled “Skin Quality – A Holistic 360° View: Consensus Results”, came to a strong consensus that skin quality can be described across all ethnicities, age groups and gender by four emergent perceptual categories (EPCs); skin tone evenness, skin surface evenness, skin firmness, and skin glow (Goldie et al., 2021). They concluded that “EPCs are composed of individual parameters, each one associated with specific measurement methods and treatment options” (Goldie et al., 2021). Despite the two studies’ slightly varied approaches to categorization, their conclusions are comparable. Skin quality is impacted by a variety of factors and multiple tissue layers. Surface quality can stem from and be impacted by deep structures or tissues, and often a multilayer treatment strategy is necessary (Goldie et al., 2021). Using the right terminology to define the issue should be accompanied with the right tools for assessing it. 

Assessment Tools

Skin quality can be measured objectively by a variety of techniques and tools. A Cutometer probe, which generates a dislocation/relaxation curve by manipulating the skin via application and release of negative pressure, is useful for measuring skin elasticity and firmness (Humphrey et al., 2021). If one isn’t available, a snap or pinch test can be used for similar assessment of tautness and elasticity (Goldie et al., 2021), as well as dermal torque meters, indentation, or angular rotation techniques. A Corneometer measures hydration “by evaluating epidermal capacitance in the stratum corneum, while other instruments measure electrical impedance to assess skin hydration” (Humphrey et al., 2021). A Mexameter is used for assessing changes in pigment or skin glow, which works by measuring light absorption and reflection to assess melanin and hemoglobin levels. Where these tools can’t probe, high-definition imaging techniques and 3D fringe projection or modeling can step in or work in conjunction to assess things such as pores and other topography. It is important to keep in mind however, that skin properties differ based on their location on the body, and as probe-based tools only analyze a small portion of skin, measurements might need to be collected and critically analyzed from multiple objective tools, combining objective and subjective photonumeric grading of skin quality parameters, for a fuller assessment – while also keeping in mind that subjective assessment tools such as clinical rating scales are generally not inclusive of all skin types or ethnicities (Humphrey et al., 2021). 

Treatment Strategies

Having a better vocabulary for describing skin quality and a framework and tools for its assessment – what can we conclude about treatment strategies? Some qualities can be improved through lifestyle adjustments; hydration can be improved by limiting sun exposure, avoiding excessive bathing, and the regular use of moisturizers (Goldie et al., 2021). Topicals are also a first-line option for improving skin quality, especially for issues with pigmentation, skin glow, and elasticity/firmness (Goldie et al., 2021). Increasing evidence shows that skin quality changes, including improvements to texture, elasticity, pliability, hydration, and oiliness, can be obtained from minimally invasive injectable procedures such as botulinum toxins and intradermal fillers (Humphrey et al., 2021).

BotulinumtoxinA (BoNT-A) formulations are particularly useful for treating skin surface evenness and glow; due to the primary mechanism of inhibiting acetylcholine release creating muscle paralysis, BoNT-A reduces wrinkles due to muscle contraction (Goldie et al., 2021). Intradermal injections can decrease sebum production improving skin laxity, and reduce the size of pores by inhibiting contraction of arrector pili muscles, though more research is needed to understand why conclusively (Goldie et al., 2021). Treatment with onabotulinum toxin A reverses the skin changes brought on by aging and UV exposure, by increasing  skin pliability and elasticity with a corresponding reduction in viscoelastic resistance (Bonaparte & Ellis, 2015). In an effort to further understand why, the study in “Alterations in the Elasticity, Pliability, and Viscoelastic Properties of Facial Skin After Injection of Onabotulinum Toxin A” hypothesized that “the dermal network of collagen may become more organized during the period when the onabotulinum toxin A is affecting the skin […] The application of onabotulinum toxin A results in increased collagen, elastin, and procollagen levels” (Bonaparte & Ellis, 2015). As more collagen and elastin is produced, it takes on features consistent with youthful skin, but after two to three months, these changes begin to wear off and skin begins to return to the characteristics normal for the individual (Bonaparte & Ellis, 2015). 

Fillers are also another powerful and minimally invasive tool that improve and/or maintain good skin quality. Hyaluronic Acid (HA) can revitalize skin texture by increasing dermal hydration and production of collagen and elastin,  improving skin elasticity, firmness, tone, glow, hydration, tightness, enlarged pores, under eye pigmentation, skin tone evenness, coloration, and glow (Goldie et al., 2021). Calcium Hydroxylapatite (CaHA) is a versatile biostimulator that can restore volume and contours, and likewise stimulate fibroblasts to produce collagen and elastin, manifesting in improvements in wrinkles, elasticity, tightness, pore size, crepiness, scars, pigmentation and more by harnessing the skin’s natural processes (Goldie et al., 2021). CaHA has also been increasingly used in a “diluted or hyper diluted form as a biostimulatory agent rather than a volumizing filler to improve skin quality and firmness for both the face and body” (Goldie et al., 2021). 

Conclusion

Modern characteristics of skin evolved due to considerations of health, disease, and sexual selection (Humphrey et al., 2021). Our relative hairlessness evolved to ward off parasites, while variations in skin pigment is a direct response to the amount of exposure to ultraviolet (UV) rays, with those living in geographical areas with consistently high UV exposure produced increased melanin as a means of photoprotection, and paler skin evolved for enhanced vitamin D synthesis for lower-light environments. As such, ethnicity and sex is important to consider when judging skin quality as well. The effects of aging differ across skin phototypes, “with lighter skin more prone to depigmentation, atrophic changes, and skin cancers, and darker skin more prone to hypertrophic skin changes, deep wrinkles, and skin thickening” (Humphrey et al., 2021). Research suggests skin qualities can be described universally by three or four emergent perceptual categories, but data is still limited elucidating skin quality parameters meant to guide practitioners in treating concerns around skin appearance and desired skin renovation. The parameters of the presented studies and the corresponding tools for evaluation will hopefully lead to more precise treatments, increasingly favourable results, and continued conversation around defining skin quality.

References

Humphrey S, Manson Brown S, Cross SJ, Mehta R. Defining Skin Quality: Clinical Relevance, Terminology, and Assessment. Dermatol Surg. 2021 Jul 1;47(7):974-981. doi: 10.1097/DSS.0000000000003079. PMID: 34148998; PMCID: PMC8231670.

Goldie K, Kerscher M, Fabi SG, Hirano C, Landau M, Lim TS, Woolery-Lloyd H, Mariwalla K, Park JY, Yutskovskaya Y. Skin Quality – A Holistic 360° View: Consensus Results. Clin Cosmet Investig Dermatol. 2021 Jun 14;14:643-654. doi: 10.2147/CCID.S309374. PMID: 34163203; PMCID: PMC8214518.

James P. Bonaparte and David Ellis. Alterations in the Elasticity, Pliability, and Viscoelastic Properties of Facial Skin After Injection of Onabotulinum Toxin A. JAMA Facial Plastic Surgery.Jul 2015.256-263. http://doi.org/10.1001/jamafacial.2015.0376