People of skin of colour comprise the majority of the world's population and Asian subjects comprise more than half of the total population of the earth. Even so, the literature on the characteristics of the subjects with skin of colour is limited. Several groups over the past decades have attempted to decipher the underlying differences in skin structure and function in different ethnic skin types. However, most of these studies have been of small scale and in some studies interindividual differences in skin quality overwhelm any racial differences. There has been a recent call for more studies to address genetic together with phenotypic differences among different racial groups and in this respect several large-scale studies have been conducted recently. The most obvious ethnic skin difference relates to skin colour which is dominated by the presence of melanin. The photoprotection derived from this polymer influences the rate of the skin aging changes between the different racial groups. However, all racial groups are eventually subjected to the photoaging process. Generally Caucasians have an earlier onset and greater skin wrinkling and sagging signs than other skin types and in general increased pigmentary problems are seen in skin of colour although one large study reported that East Asians living in the U.S.A. had the least pigment spots. Induction of a hyperpigmentary response is thought to be through signaling by the protease-activated receptor-2 which together with its activating protease is increased in the epidermis of subjects with skin of colour. Changes in skin biophysical properties with age demonstrate that the more darkly pigmented subjects retaining younger skin properties compared with the more lightly pigmented groups. However, despite having a more compact stratum corneum (SC) there are conflicting reports on barrier function in these subjects. Nevertheless, upon a chemical or mechanical challenge the SC barrier function is reported to be stronger in subjects with darker skin despite having the reported lowest ceramide levels. One has to remember that barrier function relates to the total architecture of the SC and not just its lipid levels. Asian skin is reported to possess a similar basal transepidermal water loss (TEWL) to Caucasian skin and similar ceramide levels but upon mechanical challenge it has the weakest barrier function. Differences in intercellular cohesion are obviously apparent. In contrast reduced SC natural moisturizing factor levels have been reported compared with Caucasian and African American skin. These differences will contribute to differences in desquamation but few data are available. One recent study has shown reduced epidermal Cathepsin L2 levels in darker skin types which if also occurs in the SC could contribute to the known skin ashing problems these subjects experience. In very general terms as the desquamatory enzymes are extruded with the lamellar granules subjects with lowered SC lipid levels are expected to have lowered desquamatory enzyme levels. Increased pores size, sebum secretion and skin surface microflora occur in Negroid subjects. Equally increased mast cell granule size occurs in these subjects. The frequency of skin sensitivity is quite similar across different racial groups but the stimuli for its induction shows subtle differences. Nevertheless, several studies indicate that Asian skin maybe more sensitive to exogenous chemicals probably due to a thinner SC and higher eccrine gland density. In conclusion, we know more of the biophysical and somatosensory characteristics of ethnic skin types but clearly, there is still more to learn and especially about the inherent underlying biological differences in ethnic skin types.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1467-2494.2006.00302.x

Ethnic skin types: are there differences in skin structure and function?

Injections using hypodermic needles cause pain, discomfort, localised trauma and apprehension. Additionally, careful use and disposal of needles is required to avoid transmission of blood-borne pathogens. As an alternative, microneedles can facilitate drug delivery without significantly impacting on pain receptors or blood vessels that reside beneath the skin outer layers. In this study we aim to determine the pain and sensory response to the application of wet-etch silicon microneedles, when used in such a way as to reliably penetrate skin, and provide a preliminary indication of how skin responds to microneedle injury with time. Twelve subjects received single-blinded insertions of a 25-G hypodermic needle and two microneedle arrays (36 needles of 180 and 280 μm height). The optimal method for microneedle application was determined in a pilot study. Pain intensity was scored using a visual analogue scale (VAS) and sensory perception determined using an adapted McGill Pain Questionnaire Short Form. Skin penetration was determined by external staining and measurement of trans-epidermal water loss (TEWL). Mean VAS scores, verbal descriptions and questionnaire responses showed that the 180 and 280 μm microneedles caused significantly less pain and discomforting sensation in participants than the hypodermic needle. Methylene blue staining and TEWL analysis confirmed that microchannels were formed in the skin following microneedle application. Evidence of microchannel repair and resealing was apparent at 8–24 h post-application. In summary, this study shows that pyramidal wet-etch microneedles can penetrate human skin with minimal pain and sensory discomfort, creating transient pathways for potential drug, vaccine and DNA delivery.

Clinical administration of microneedles: skin puncture, pain and sensation.

https://comum.rcaap.pt/bitstream/10400.26/5927/1/Bacterial%20cellulose%20membranes%20as%20drug%20delivery%20systems.pdf

Bacterial cellulose membranes as drug delivery systems: an in vivo skin compatibility study

Racial (ethnic) differences in skin properties may explain racial disparities seen in dermatologic disorders and provide insight into appropriate differences in the management of these disorders. However, racial differences in skin have been minimally investigated by objective methods and the data are often contradictory. Objective methods studied include transepidermal water loss (TEWL), water content (WC), corneocyte variability, blood vessel reactivity, elastic recovery/extensibility, pH gradient, lipid content, surface microflora, microscopic evaluation of mast cell granules, and confocal microscopy. The majority of the evidence (six out of eight studies) indicates that TEWL is greater in Black skin compared with White skin. TEWL measurements of Asian skin are inconclusive as they have been found to be equal to Black skin and greater than Caucasian skin, equal to Caucasian skin, and less than all other ethnic groups in different studies. Racial differences in WC, as measured by resistance, capacitance, conductance and impedance, are also inconclusive as the data are contradictory. While the evidence regarding corneocyte desquamation is minimal, one clinically provocative observation is that Blacks have a 2.5 times greater spontaneous desquamation rate compared with Caucasians and Asians, possibly accounting for an increased frequency of xerosis seen clinically in Blacks. With regards to blood vessel reactivity, studies can not be compared to each other because each uses different vasoactive substances. However, each study, except for one study comparing Hispanics and Whites, and another comparing Japanese and German women, reveal some degree of racial variation in blood vessel reactivity. It has been demonstrated that the pH of Black skin is less than White skin; however, the studies that have demonstrated this have done so under different skin conditions and on different anatomic sites. Racial differences in lipid content are inconclusive. Additionally, there is insufficient and conflicting evidence to make conclusions regarding racial differences in skin biomechanics and skin microflora. Microscopic evaluation reveals that Black skin contains larger mast cell granules, and differences in stuctural properties and enzymes of mast cells compared with White skin, possibly accounting for differences in pruritus experienced by the individuals of these racial groups. There exists substantial evidence to support that Black skin has a higher TEWL, variable blood vessel reactivity, decreased skin surface pH, and larger mast cell granules compared with White skin. Although some deductions have been made about Asian and Hispanic skin, further evaluation needs to be done. Differences in WC, corneocyte desquamation, elastic recovery/extensibility, lipid content and skin microflora, although statistically significant, are inconclusive.

Racial (ethnic) differences in skin properties: the objective data.

Certain individuals experience more intense and frequent adverse sensory effects than the normal population after topical use of personal care products, a phenomenon known in popular usage as sensitive skin. Consumer reports of sensitive skin are self-diagnosed and often not verifiable by objective signs of physical irritation. Companies who manufacture cosmetic and personal care products are challenged to provide safe products to an audience with tremendous differences in skin type, culture and habits. This review examines the still incomplete understanding of this phenomenon with respect to aetiology, diagnosis, appropriate testing methods, possible contributing host factors such as, sex, ethnicity, age, anatomical site, cultural and environmental factors, and the future directions needed for research.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.0105-1873.2006.00886.x

Sensory, clinical and physiological factors in sensitive skin: a review.

Irritant patch testing with sodium lauryl sulfate (SLS) will become more and more a routine test determining skin susceptibility in men. Recently, it has been shown that for practical reasons, irritant SLS patch testing can take place on the back simultaneously with a routine allergic patch test to other contact allergens. However, SLS patch testing has mostly been performed on the forearm in studying experimental skin irritation so far. The aim of this study was to determine whether there is a relationship in skin response to aqueous SLS (0.125%; 0.25%; 0.5% and 1.0%) between the forearm and the back assessed by visual scoring and measurement of transepidermal water loss (TEWL). We found a pronounced reaction of the forearm compared to the back. TEWL values as well as visual scores correlated well with SLS concentration. There was also a high correlation in visual scoring between the forearm and the back. Based on test sensitivity and specificity we suggest a 48 hrs patch test for routine screening with 0.5% SLS on the forearm evaluated by TEWL measurement or visual scoring 24 hrs after patch removal. A mild erythema (scored as < or =1) is considered to be normal. If for practical reasons, the SLS patch is placed on the back simultaneously with the allergic patch test, 0.5% SLS may be sufficient, too. TEWL measurement so far provides a reliable method and will certainly be necessary for experimental studies on irritant skin reactions, particularly when different SLS concentrations are used. After a 48 hrs patch test with SLS 0.5% TEWL measurement should be performed at 72 hrs. A value of < or =31.6 g/m(2)hr seems to follow the normal distribution.

Evaluation of skin susceptibility to irritancy by routine patch testing with sodium lauryl sulfate

For testing with sodium lauryl sulphate (SLS), measurements of transepidermal water loss (TEWL) and cutaneous blood flow with laser Doppler (LD) are considered to be the most reliable methods. The aim of this study was to determine which method of measurement should be preferred when conducting SLS testing under varying conditions. Patch testing with SLS at different concentrations and exposure times was performed. TEWL values were compared with those of LD. TEWL values showed distinct changes at low SLS concentrations and short application periods. By contrast, higher SLS concentrations were necessary to increase LD values. Short application of patches changed TEWL rather than LD values. When evaluating SLS patch testing by bioengineering methods, TEWL measurement appears to be more suitable for a test procedure that provokes mild skin reactions (SLS concentration or=1%).

Which bioengineering assay is appropriate for irritant patch testing with sodium lauryl sulfate

Allergic contact dermatitis due to diethyl sebacate

changes are apparent, a thermal stimulus may lead to anincrease in TSBF. This phenomenon can also be seen afterbiophysical skin parameters and the SLS concentration (0%, water application, which is a weak irritant (18). While TEWL0.25%and0.5%). The higher the SLS concentration, the did not signi® cantly increase, the blood ¯ ow after thermalhigher the values of TEWL, chromameter-a* and LD. After stimulus increased markedly, indicating that an increasedthermal stimulation the SLS-irritated skin reacts (depending TSBF is a phenomenon also observable in mildly irritatedon SLS concentration) with an abrupt increase in blood ¯ ow skin. This phenomenon may explain early in¯ ammatory signs(Fig. 1). The time period until reaching a steady state of blood on irritated hands due to work in hot environments (e.g.¯ ow is shortened, and hence the slope of the curve rises kitchen, furnace, etc.).(Fig. 1). The diŒerences in TSBF values between basal areas As any in¯ ammatory process is followed by increased blood(no patch test) and SLS-patch areas weresigni® cant (

Response to Thermal Stimuli in Skin Pretreated with Sodium

Background It is well known that the degree of skin reaction to an irritant depends on its concentration and exposure time.



Objectives To determine the interrelationship between the concentration of sodium lauryl sulphate (SLS) and exposure time in both weak (subclinical) and severe reactions.



Methods Patch testing with SLS was performed at different concentrations (0·125%, 0·25%, 0·5%, 1·0% and 2·0%) and with different exposure times (3, 6, 12, 24 and 48 h). Evaluation was conducted by measurement of transepidermal water loss and by laser-Doppler flowmetry both 30 min and 24 h after patch removal.



Results We found more reliable and constant skin reactions 24 h after patch removal, and a higher correlation between SLS concentration and skin reaction.



Conclusions We conclude that the concentration of SLS influences the test outcome to a larger degree than the exposure time. We present formulae by which the outcome of SLS patch testing at various SLS concentrations ranging from 0·125% to 2% and any exposure time between 3 and 24 h can be estimated.

Irritant patch testing with sodium lauryl sulphate: interrelation between concentration and exposure time.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Jun Aramaki

Author Tools

Chat about Author