Systematic review of the use of platelet-rich plasma in aesthetic dermatology

Platelet-rich plasma (PRP) is a highly concentrated autologous solution of plasma prepared from a patient's own blood. PRP contains platelets that are purported to release numerous growth factors that may be valuable in numerous dermatologic applications. Here, we review systematically the clinical cosmetic applications of PRP including: androgenetic alopecia, scar revision, acne scars, skin rejuvenation, dermal augmentation, and striae distensae to understand the potential and best practices for PRP use. A systematic search was conducted on three databases: Pubmed, Embase, and Web of Science. Publications were included if they were in English, investigated the clinical applications of PRP in aesthetic dermatology and reported clinical results either as case reports or clinical studies. There were a total of 22 manuscripts that fulfilled these criteria. Four evaluated hair-related applications, eight evaluated the treatment of scars and postprocedure recovery, eight evaluated skin rejuvenation and dermal augmentation, and two evaluated treatment of striae distensae. PRP is a relatively new treatment modality with studies suggesting its utility in aesthetic dermatology. The combination of PRP with other therapies is particularly interesting. Future studies should include controls, including incorporation of split-face comparisons, to reduce intersubject variability.

Alopecia as the Presenting Symptom of Syphilis

Alopecia can be one of the many symptoms of secondary syphilis and the clinical presentations include essential syphilitic alopecia or symptomatic syphilitic alopecia. In this report, we present a case of a patient with essential syphilitic alopecia whose sole presenting symptom of syphilis was alopecia. Despite an initial negative rapid plasma reagin (RPR) test, he was ultimately found to have syphilis on scalp biopsy. His alopecia improved following treatment with benzathine penicillin. This presentation serves as a reminder to clinicians to be cognizant of alopecia as a presenting sign of syphilis. A review of the specificity and sensitivity of the typical tests used for the diagnosis is presented.

The association of the sebum excretion rate with melasma, erythematotelangiectatic rosacea, and rhytides

BACKGROUND

Rosacea and melasma are two common skin conditions in dermatology. Both conditions have a predilection for the centrofacial region where the sebaceous gland density is the highest. However it is not known if sebaceous function has an association with these conditions.

AIMS AND OBJECTIVES

We aimed to assess the relationship between facial glabellar wrinkle severity and facial sebum excretion rate for individuals with rosacea, melasma, both conditions, and in those with rhytides. Secondly, the purpose of this study was to utilize high resolution 3D facial modeling and measurement technology to obtain information regarding glabellar rhytid count and severity.

MATERIALS AND METHODS

A total of 21 subjects participated in the study. Subjects were divided into four groups based on facial features: rosacea-only, melasma-only, rosacea and melasma, rhytides-only. A high resolution facial photograph was taken followed by measurement of facial sebum excretion rate (SER).

RESULTS

The SER was found to decline with age and with the presence of melasma. The SER negatively correlated with increasing Wrinkle Severity Rating Scale. Through the use of 3D facial modeling and skin analysis technology, we found a positive correlation between clinically based grading scores and computer generated glabellar rhytid count and severity.

CONCLUSION

Continuing research with facial modeling and measurement systems will allow for development of more objective facial assessments. Future studies need to assess the role of technology in stratifying the severity and subtypes of rosacea and melasma. Furthermore, the role of sebaceous regulation may have important implications in photoaging.

Effects of Fermented Dairy Products on Skin: A Systematic Review

OBJECTIVE

Fermented dairy products, such as yogurt, have been proposed as a natural source of probiotics to promote intestinal health. Growing evidence shows that modulation of the gastrointestinal tract microbiota can modulate skin disease as well. This systematic review was conducted to examine the evidence for the use of ingested fermented dairy products to modulate skin health and function. We also sought to review the effects of the topical application of dairy products.

DESIGN

The PubMed and Embase databases were systematically searched for clinical studies involving humans only that examined the relationship between fermented dairy products and skin health.

RESULTS

A total of 312 articles were found and a total of 4 studies met inclusion criteria. Three studies evaluated the effects of ingestion, while one evaluated the effects of topical application. All studies noted improvement with the use of fermented dairy.

CONCLUSIONS

Overall, there is early and limited evidence that fermented dairy products, used both topically and orally, may provide benefits for skin health. However, existing studies are limited and further studies will be important to better assess efficacy and the mechanisms involved.

Evaluating clinical trial design: systematic review of randomized vehicle-controlled trials for determining efficacy of benzoyl peroxide topical therapy for acne

Determined efficacies of benzoyl peroxide may be affected by study design, implementation, and vehicle effects. We sought to elucidate areas that may allow improvement in determining accurate treatment efficacies by determining rates of active treatment and vehicle responders in randomized controlled trials assessing the efficacy of topical benzoyl peroxide to treat acne. We conducted a systematic review of randomized vehicle-controlled trials evaluating the efficacy of topical benzoyl peroxide for the treatment of acne. We compared response rates of vehicle treatment arms versus those in benzoyl peroxide arms. Twelve trials met inclusion criteria with 2818 patients receiving benzoyl peroxide monotherapy treatment and 2004 receiving vehicle treatment. The average percent reduction in total number of acne lesions was 44.3 (SD = 9.2) and 27.8 (SD = 21.0) for the active and vehicle treatment groups, respectively. The average reduction in non-inflammatory lesions was 41.5 % (SD = 9.4) in the active treatment group and 27.0 % (SD = 20.9) in the vehicle group. The average percent decrease in inflammatory lesions was 52.1 (SD = 10.4) in the benzoyl peroxide group and 34.7 (SD = 22.7) in the vehicle group. The average percentage of participants achieving success per designated study outcomes was 28.6 (SD = 17.3) and 15.2 (SD = 9.5) in the active treatment and vehicle groups, respectively. Patient responses in randomized controlled trials evaluating topical acne therapies may be affected by clinical trial design, implementation, the biologic effects of vehicles, and natural disease progression. "No treatment" groups may facilitate determination of accurate treatment efficacies.

Squamous cell carcinoma in the setting of chronic hidradenitis suppurativa; report of a patient and update of the literature

Squamous cell carcinoma (SCC) developing in chronic hidradenitis suppurativa (HS) is rare, but failing to recognize the condition may have significant consequences. Dermatologists must be aware of the potential for malignant transformation and should have a low threshold for biopsy when clinical presentation is atypical. Herein we describe a 64-year-old woman with metastatic vulvar SCC that developed within an area of chronic HS. Like SCC associated with other chronic inflammatory disorders (Marjolin's ulcers), mortality is significant. Past reviews have reported death rates above 40% and our most recent update continues to support poor prognoses for these patients.

Photoprotective effect of botanicals and vitamins: A systematic review of clinical trials

BACKGROUND

Overexposure to solar radiation is a major contributor to skin cancer development and premature skin aging. Botanical extracts and vitamins may represent novel photoprotective agents.

OBJECTIVE

We sought to systemically review clinical evidence for the use of botanically derived agents and vitamins as photoprotective agents.

METHODS

We systematically searched Embase and PubMed databases. Two independent reviewers reviewed abstracts for inclusion. Additional relevant studies were identified by a manual review of reference lists. Data from eligible studies were extracted independently and discrepancies were resolved by consensus.

RESULTS

A total of 51 studies met inclusion criteria. Limited available evidence indicates that several botanical agents and vitamins in topical or oral forms may have promising photoprotective effects. However, generalizability of results is limited by small sample sizes.

CONCLUSION AND RELEVANCE

Botanical extracts and vitamins may add to the armamentarium of sun-protective agents. Additional high-quality trials are needed to strengthen support for their use.

Eicosanoids and Keratinocytes in Wound Healing

Significance: Eicosanoids are biologically active lipid mediators derived from arachidonic acid that are important in injury and inflammatory responses. Cyclooxygenase-1 and cyclooxygenase-2 mediate the production of prostanoids, whereas 5-lipoxygenase mediates the production of leukotrienes and hydroxyeicosatetraenoic acids. These lipid mediators have traditionally been known to recruit cells of the immune system to a site of injury and inflammation. However, they also interact with various cells that are resident to the wound bed, including modulation of keratinocyte activity. Recent Advances: Recent work has identified multiple prostanoid and leukotriene receptors on keratinocytes, indicating that eicosanoids directly interact with them. Recent work also shows that keratinocytes are capable of producing prostanoids and leukotrienes. Critical Issues: Much of the critical work has been performed in cell culture and mouse in vivo models. This has greatly expanded our understanding of the eicosanoid interactions with keratinocytes and wound healing in general. However, few of these in vivo models have been able to critically evaluate keratinocyte migration and re-epithelialization. Future Directions: As research continues in this exciting field, the cellular pathways stimulated by the eicosanoids will become better defined. Future research with excisional wound models in mice and pigs and ex vivo human skin models will better isolate the contribution of eicosanoid-mediated effects on keratinocyte migration and re-epithelialization.

The economic burden of sunscreen usage

Excessive sun exposure is known to be the leading cause of skin cancer. The direct cellular damage inflicted by the ultraviolet (UV) radiation from the sun results in premature aging, DNA damage, and mutations that ultimately lead to skin cancer. Sunscreens are highly recommended to protect against UV radiation. However, little research has been conducted on the economic burden of sunscreen use. In this study, we aimed to evaluate the annual cost of sunscreen under both ideal and actual use conditions while stratifying for the sun protection factor (SPF) and by the name brand or equivalent store brand sunscreen. Pricing data was collected for sunscreens of SPF 30, 50, 70, and 100. For each type of sunscreen, the size and price of the container were recorded. Our results demonstrated that sunscreen prices increased with SPF but purchasing a generic sunscreen resulted in savings of 40%-50%. Our estimates reveal that sunscreens are affordable with annual expenditures ranging from $30.21 to $61.94, depending on brand, for SPF 50 sunscreens used with minimal application density for the average person.

UVB-sensitive solar urticaria possibly associated with terbinafine

Solar urticaria is an uncommon condition characterized by erythema and whealing shortly after exposure to ultraviolet (UV) and/or visible light. We report a 25-year-old woman with an erythematous, edematous, pruritic reaction minutes after sun exposure while she was taking terbinafine for onychomycosis. Phototesting revealed a UVB-sensitive urticarial reaction, confirming the diagnosis of solar urticaria. This report describes the first patient with possible terbinafine-associated solar urticaria.

The use of botanically derived agents for hyperpigmentation: a systematic review

BACKGROUND

Hyperpigmentation disorders are common among those seeking care from dermatologists and primary care physicians. The cosmeceutical and natural product industries are rapidly growing and many botanical agents are purported to improve hyperpigmentation disorders.

OBJECTIVE

We sought to review clinical evidence for the use of botanical agents in the treatment of hyperpigmentation.

METHODS

We searched MEDLINE and Embase databases and a total of 26 articles met inclusion criteria. Study methodology was analyzed and the reproducibility of the studies was graded.

RESULTS

Several botanical agents appear promising as treatment options but few studies were methodologically rigorous. Several plant extract and phytochemicals effectively lighten signs of epidermal melasma and hyperpigmentation induced by ultraviolet radiation exposure. Results were mixed for treatment of solar lentigines or dermal hyperpigmentation.

LIMITATIONS

There were few rigorously designed studies; future research will be critical to further ascertain the discussed results.

CONCLUSIONS

The subtype of hyperpigmentation is important for treatment prognosis, with dermal hyperpigmentation less responsive to treatment. Botanical extracts may play an integrative role in the treatment of hyperpigmentation and further studies that integrate them with standard therapies are needed. Side effects, including worsened hyperpigmentation, need to be discussed when considering these therapies.

A case of Drug Rash with Eosinophilia and Systemic Symptoms (DRESS) related to rufinamide

Drug Rash (or Reaction) with Eosinophilia and Systemic Symptoms (DRESS) is a potentially life-threatening hypersensitivity reaction to drugs characterized by rash, fever, lymphadenopathy, hematologic abnormalities, and involvement of internal organs. Initially coined in 1996, the term is used to refer to an idiosyncratic reaction to several drugs, the most common of which are carbamazepine, allopurinol, sulfasalazine, and phenobarbital. We report the first case of DRESS related to rufinamide in a ten year old boy with a history of a complex seizure disorder.

Effective Strategies for the Management of Pyoderma Gangrenosum

BACKGROUND

Pyoderma gangrenosum (PG) is an inflammatory disease characterized by painful ulcerations. It is often associated with other systemic inflammatory diseases, especially inflammatory bowel disease (IBD) and autoimmune arthritis.

THE PROBLEM

PG does not have characteristic serologic or histologic features. Therefore, other potential causes such as malignancy, vasculitis, infection, and coagulation disorders should be ruled out. In addition, patients often have aggressive disease that is refractory to immunosuppressive therapy, but there is only a paucity of clinical data to help direct therapy.

BASIC/CLINICAL SCIENCE ADVANCES

There are several lines of evidence to support an immunologic etiology of PG. Although the pathogenesis is still not well understood, it is clear that PG is associated with the upregulation of several cytokines including interleukin 8 (IL-8), tumor necrosis factor (TNF), IL-1β, IL-6, and interferon gamma, among many others. TNF and IL-1β are of particular interest, because some biologic medications that target these cytokines have been effective in treating PG.

CLINICAL CARE RELEVANCE

Multiple drugs are available to help control PG. Biologics, intravenous immunoglobulin (IVIG), and conventional immunosuppressive drugs have been reported to be effective. Multidrug therapies should be considered for refractory cases.

CONCLUSION

PG is a complex inflammatory disease with multiple involved pathways. Anti-TNF agents and IVIG represent a significant advancement in treatment options. Since some biologic therapies are relatively new, their unknown long-term side effects should be taken into consideration.

Phytochemicals and Naturally Derived Substances for Wound Healing

BACKGROUND

Complementary and alternative medicines (CAMs) are widely used by the general public. Natural products including plant-derived extracts (phytochemicals) and naturally derived substances, such as honey, are an important component of CAM. Here, we review the evidence for their use in wound care.

THE PROBLEM

Wound healing is complex and disruption of this process can lead to considerable morbidity, including chronic wounds, infection, and scarring. Natural products have a long history of use in wound care, but there are only a few rigorous studies. With the growing interest in the use of natural products and the belief that they are safer than standard therapies, it is vital to understand the current knowledge of their efficacy and side effects.

BASIC/CLINICAL SCIENCE ADVANCES

Natural products possess antioxidant, anti-inflammatory, angiogenic, and cell synthesis-modulating components among many others. However, this complex composition of chemicals may increase the risk for irritant or allergic side effects.

CLINICAL CARE RELEVANCE

Natural products can be much cheaper than conventional treatments, but further study is needed to better understand their efficacy. The type of wound and the potential for side effects need to be carefully considered when choosing a treatment.

CONCLUSION

The research to date is supportive of the use of natural products in wound care. Patients need to be cautioned of potential side effects. Collaborative research between allopathic medicine and medical systems that frequently employ phytochemicals and naturally derived substances, such as Ayurveda and naturopathy, will provide a better understanding of how to integrate natural products into wound care.

A novel keratin 5 mutation in a familial cluster

We report a case of epidermolysis bullosa simplex (EBS) associated with a family cluster of EBS and a novel KRT5 mutation. The case is presented in the context of recent advances in the study of the disease.

Unilateral calciphylaxis in a patient with systemic lupus erythematosus, chronic kidney disease, and hemodialysis-associated steal syndrome

Calciphylaxis is a rare but life-threatening disease characterized by deposition of calcium within small and medium sized vessels, with subsequent thrombosis, cutaneous ischemia, and necrosis. Because of its systemic nature, calciphylaxis is typically a symmetrical, bilaterally-distributed phenomenon. Here, we present an unusual case of unilateral leg calciphylaxis in the setting of relative chronic arterial insufficiency of the affected extremity secondary to steal syndrome.

Biological therapy of psoriasis

The treatment of psoriasis has undergone a revolution with the advent of biologic therapies, including infliximab, etanercept, adalimumab, efalizumab, and alefacept. These medications are designed to target specific components of the immune system and are a major technological advancement over traditional immunosuppressive medications. These usually being well tolerated are being found useful in a growing number of immune-mediated diseases, psoriasis being just one example. The newest biologic, ustekinumab, is directed against the p40 subunit of the IL-12 and IL-23 cytokines. It has provided a new avenue of therapy for an array of T-cell-mediated diseases. Biologics are generally safe; however, there has been concern over the risk of lymphoma with use of these agents. All anti-TNF-α agents have been associated with a variety of serious and “routine” opportunistic infections.

Keratinocyte proximity and contact can play a significant role in determining mesenchymal stem cell fate in human tissue

Bone marrow-derived human mesenchymal stem cells (hMSCs) possess multipotent differentiation capabilities and are a potent source of paracrine factors. We show how the epidermal keratinocyte can direct hMSC differentiation selectively. Keratinocytes and hMSCs were either cocultured in physical contact (contact cocultures), or separated without physical contact using a transwell insert (noncontact cocultures). We also delivered hMSCs into an ex vivo human excisional wound where subpopulations of the hMSCs were either in contact or were physically separated from the epidermal keratinocytes. In comparison to control hMSCs that were not cocultured, contact cocultured hMSCs adopted an epithelial morphology and expressed keratinocyte markers while noncontact cocultured hMSCs, surprisingly, adopted phenotypes that resembled myofibroblast and early neural lineage, both of which are of dermal origin. Cell fusion was not a requirement in in vitro contact cocultures, as determined by fluorescence-activated cell sorting (FACS) and fluorescence in situ hybridization analysis (FISH). To the best of our knowledge, this work provides the first example of hMSC differentiation into different lineages depending on their proximity to a single cell type.

Advice for medical students interested in dermatology: perspectives from fourth year students who matched

We present perspectives from four fourth year medical students who matched into dermatology that highlight the factors they believed helped them most. The purpose is to offer advice to medical students interested in dermatology. We divide the paper into four areas of discussion: academics, extracurricular activities, research, and mentorship. All four factors are crucial for a strong dermatology application. We believe the paper provides valuable suggestions and guidance to students considering a career in dermatology.

The benefits and risks of ultraviolet tanning and its alternatives: the role of prudent sun exposure

Sunlight- and indoor ultraviolet (UV)-induced tanning is a common behavior, especially among adolescents, young adults, and individuals who have lighter skin. Excessive sun exposure is associated with several health risks, including the acceleration of skin aging and the promotion of skin cancers. Several health benefits of UV exposure include vitamin D production and improved mood. This article analyzes these health risks and benefits and discusses pertinent issues surrounding indoor tanning, the role of sunless tanning products, and prudent sun exposure.

Stress-mediated increases in systemic and local epinephrine impair skin wound healing: potential new indication for beta blockers

BACKGROUND

Stress, both acute and chronic, can impair cutaneous wound repair, which has previously been mechanistically ascribed to stress-induced elevations of cortisol. Here we aimed to examine an alternate explanation that the stress-induced hormone epinephrine directly impairs keratinocyte motility and wound re-epithelialization. Burn wounds are examined as a prototype of a high-stress, high-epinephrine, wound environment. Because keratinocytes express the beta2-adrenergic receptor (beta2AR), another study objective was to determine whether beta2AR antagonists could block epinephrine effects on healing and improve wound repair.

METHODS AND FINDINGS

Migratory rates of normal human keratinocytes exposed to physiologically relevant levels of epinephrine were measured. To determine the role of the receptor, keratinocytes derived from animals in which the beta2AR had been genetically deleted were similarly examined. The rate of healing of burn wounds generated in excised human skin in high and low epinephrine environments was measured. We utilized an in vivo burn wound model in animals with implanted pumps to deliver beta2AR active drugs to study how these alter healing in vivo. Immunocytochemistry and immunoblotting were used to examine the up-regulation of catecholamine synthetic enzymes in burned tissue, and immunoassay for epinephrine determined the levels of this catecholamine in affected tissue and in the circulation. When epinephrine levels in the culture medium are elevated to the range found in burn-stressed animals, the migratory rate of both cultured human and murine keratinocytes is impaired (reduced by 76%, 95% confidence interval [CI] 56%-95% in humans, p < 0.001, and by 36%, 95% CI 24%-49% in mice, p = 0.001), and wound re-epithelialization in explanted burned human skin is delayed (by 23%, 95% CI 10%-36%, p = 0.001), as compared to cells or tissues incubated in medium without added epinephrine. This impairment is reversed by beta2AR antagonists, is absent in murine keratinocytes that are genetically depleted of the beta2AR, and is reproduced by incubation of keratinocytes with other beta2AR-specific agonists. Activation of the beta2AR in cultured keratinocytes signals the down-regulation of the AKT pathway, accompanied by a stabilization of the actin cytoskeleton and an increase in focal adhesion formation, resulting in a nonmigratory phenotype. Burn wound injury in excised human skin also rapidly up-regulates the intra-epithelial expression of the epinephrine synthesizing enzyme phenylethanolamine-N-methyltransferase, and tissue levels of epinephrine rise dramatically (15-fold) in the burn wounded tissue (values of epinephrine expressed as pg/ug protein +/- standard error of the mean: unburned control, 0.6 +/- 0.36; immediately postburn, 9.6 +/- 1.58; 2 h postburn, 3.1 +/- 1.08; 24 h post-burn, 6.7 +/- 0.94). Finally, using an animal burn wound model (20% body surface in mice), we found that systemic treatment with betaAR antagonists results in a significant increase (44%, 95% CI 27%-61%, p < 0.00000001) in the rate of burn wound re-epithelialization.

CONCLUSIONS

This work demonstrates an alternate pathway by which stress can impair healing: by stress-induced elevation of epinephrine levels resulting in activation of the keratinocyte beta2AR and the impairment of cell motility and wound re-epithelialization. Furthermore, since the burn wound locally generates epinephrine in response to wounding, epinephrine levels are locally, as well as systemically, elevated, and wound healing is impacted by these dual mechanisms. Treatment with beta adrenergic antagonists significantly improves the rate of burn wound re-epithelialization. This work suggests that specific beta2AR antagonists may be apt, near-term translational therapeutic targets for enhancing burn wound healing, and may provide a novel, low-cost, safe approach to improving skin wound repair in the stressed individual.

Beta adrenergic receptors in keratinocytes

Beta2 adrenergic receptors were identified in keratinocytes more than 30 years ago, but their function in the epidermis continues to be elucidated. Abnormalities in their expression, signaling pathway, or in the generation of endogenous catecholamine agonists by keratinocytes have been implicated in the pathogenesis of cutaneous diseases such as atopic dermatitis, vitiligo, and psoriasis. New studies also indicate that the beta2AR also modulates keratinocyte migration, and thus can function to regulate wound reepithelialization. This review focuses on the function of these receptors in keratinocytes and their contribution to cutaneous physiology and disease.

Microneedles and transdermal applications

With the limitations of oral drug delivery and the pain and needle phobias associated with traditional injections, drug delivery research has focused on the transdermal delivery route. A formidable barrier to transdermal drug delivery is the stratum corneum, the superficial layer of the skin. In the last 10 years, microneedles were proposed as a mechanical tool to pierce through the stratum corneum, in order to create drug delivery channels without stimulating underlying pain nerves. Since then, the field of microneedles has rapidly evolved to spawn a plethora of potential transdermal applications. In this review, the authors provide an overview of the progress in microneedle research and design, and the advancements that have been made in employing this technology for transdermal applications.

Clinical microneedle injection of methyl nicotinate: stratum corneum penetration

BACKGROUND/PURPOSE

In recent years, microneedles were proposed as a method to painlessly deliver drugs past the stratum corneum. Microneedles have been fabricated in several designs, but limited studies have tested microneedle injections in humans. In this work, we compare microneedle injections with topical application (TA) to investigate if microneedles enhance in vivo drug delivery past the stratum corneum.

METHOD

In vitro tests were used to measure microneedle pressures and injection volumes. In vivo microneedle injections were performed on the volar forearm of 11 healthy volunteers. Two sets of microneedles, pointed and symmetric, were used to develop microneedle/syringe apparatuses that were used to inject approximately 1 microL of 0.1 M methyl nicotinate, and were compared against TA. A Laser Doppler Perfusion Monitor was used to record maximum blood flow and the time to maximum blood flow at the treatment sites.

RESULTS

Pointed and symmetric microneedle-injected sites showed a significantly faster time to maximum blood flow than TA. The pointed microneedle injections also resulted in a higher maximum blood flux. Volunteers reported feeling pressure but no pain from the microneedles during the injections.

CONCLUSION

The microneedles aid in bypassing the stratum corneum and enhance drug delivery through it. The design of the microneedle influences its delivery capabilities, because the pointed microneedles seem to be less susceptible to clogging during the injection.

Tribological testing of skin products: gender, age, and ethnicity on the volar forearm

BACKGROUND/PURPOSE

Few studies have focused on the simultaneous measurement of the friction and electrical properties of skin. This work investigates the feasibility of using these measurements to differentiate between the effects of chemicals commonly applied to the skin. In addition, this study also compares the condition of the skin and its response to application of chemicals across gender, ethnicity, and age at the volar forearm.

METHOD

Friction and electrical tests were performed on 59 healthy volunteers with the UMT Series Micro-Tribometer (UMT). A 13-mm-diameter copper cylindrical friction/electrical probe was pressed onto the skin with a weight of 20 g and moved across the skin at a constant velocity of 0.4 mm/s. Each volunteer served as his or her own control. The friction and electrical impedance measurements were performed for polyvinylidene chloride occlusion and for the application of glycerin and petrolatum.

RESULTS

No differences were found across age, gender, or ethnicity at the volar forearm. Polyvinylidene chloride (PVDC) occlusion showed a small increase in the friction and a small decrease in the electrical impedance; petrolatum increased the friction by a greater amount but its effect on the impedance was comparable to PVDC occlusion; glycerin increased the friction by an amount comparable to petrolatum, but it decreased the impedance to a much greater degree than petrolatum or the PVDC occlusion. An amplitude/mean measurement of the friction curves of glycerin and petrolatum showed that glycerin has a significantly higher amplitude/mean than petrolatum.

CONCLUSION

The properties of the volar forearm appear to be independent of age, gender, and ethnicity. Also, the simultaneous measurement of friction and electrical impedance was useful in differentiating between compounds administered to the skin.

Friction coefficient of skin in real-time

BACKGROUND/PURPOSE

Friction studies are useful in quantitatively investigating the skin surface. Previous studies utilized different apparatuses and materials for these investigations but there was no real-time test parameter control or monitoring. Our studies incorporated the commercially available UMT Series Micro-Tribometer, a tribology instrument that permits real-time monitoring and calculation of the important parameters in friction studies, increasing the accuracy over previous tribology and friction measurement devices used on skin.

METHODS

Our friction tests were performed on four healthy volunteers and on abdominal skin samples. A stainless steel ball was pressed on to the skin with at a pre-set load and then moved across the skin at a constant velocity of 5 mm/min. The UMT continuously monitored the friction force of the skin and the normal force of the ball to calculate the friction coefficient in real-time. Tests investigated the applicability of Amonton's law, the impact of increased and decreased hydration, and the effect of the application of moisturizers.

RESULTS

The friction coefficient depends on the normal load applied, and Amonton's law does not provide an accurate description for the skin surface. Application of water to the skin increased the friction coefficient and application of isopropyl alcohol decreased it. Fast acting moisturizers immediately increased the friction coefficient, but did not have the prolonged effect of the slow, long lasting moisturizers.

CONCLUSION

The UMT is capable of making real-time measurements on the skin and can be used as an effective tool to study friction properties. Results from the UMT measurements agree closely with theory regarding the skin surface.

Coefficient of friction: tribological studies in man - an overview

BACKGROUND/PURPOSE

Compared to other studies of skin, relatively few studies have focused on the friction of skin. This work reviews existing skin friction, emphasizing test apparatuses and parameters that have added to information regarding the friction coefficient. This review also outlines what factors are important to consider in future friction studies.

METHODS

Past studies have utilized numerous designs for a test apparatus, including probe geometry and material, as well as various probe motions (rotational vs. linear). Most tests were performed in vivo; a few were performed in vitro and on porcine skin.

RESULTS

Differences in probe material, geometry and smoothness affect friction coefficient measurements. An increase in skin hydration, either through water or through moisturizer application, increases its friction coefficient; a decrease in skin hydration, either through clinical dermatitis or through alcohol addition, decreases the coefficient. Differences are present between anatomical sites. Conflicting results are found regarding age and no differences are apparent as a result of gender or race.

CONCLUSION

Skin friction appears to be dependent on several factors - such as age, anatomical site and skin hydration. The choice of the probe and the test apparatus also influence the measurement.