Effects of skin occlusion on percutaneous absorption: an overview

Skin occlusion produces profound changes, including hydration status, barrier permeability, epidermal lipids, DNA synthesis, microbial flora, and numerous molecular and cellular processes. It often, but not always, increases percutaneous absorption of applied chemicals. This overview focuses on the effect of skin occlusion on percutaneous absorption.     

Effects of skin occlusion in patch testing with sodium lauryl sulphate

BACKGROUND: When evaluating transepidermal water loss (TEWL) in patch testing, the occlusive effect of the patch must be considered as an important artificial impairment of the measurement. OBJECTIVES: To investigate the time course of effects of occlusion. METHODS: Epicutaneous patches with sodium lauryl sulphate (SLS) 0.25%, SLS 0.5%, water and an empty test chamber (control) were applied on the volar forearm for different time intervals (12, 24, 48 h). Test reactions were evaluated by measurement of TEWL immediately, every 15 min during the first hour, every 30 min during the following 3 h and 24 h after patch removal. RESULTS: After patch removal, TEWL values showed a steep increase. When compared with basal values, TEWL values after SLS patch testing remained increased for 24 h, whereas TEWL values on water patch sites were only significantly increased for up to 180 min, and on empty patch sites for only up to 120 min after patch removal. The prolonged increase in TEWL values in SLS patch testing seemed to be induced by barrier function damage caused by SLS itself, as shown in various earlier studies. After the initial increase, TEWL values showed a significant decrease for all patches from 0 to 120 min after patch removal. Patch testing with water gave a significant decrease in TEWL values up to 180 min, and for empty chambers (control) up to 150 min after removal of patches. These data suggest that the occlusive effect on TEWL in patch testing ends 3 h after the removal of test chambers. CONCLUSIONS: We recommend TEWL measurement in SLS patch testing after a period of at least 3 h after patch removal. For practical purposes a 24-h period after patch removal may be useful.     

Effect of occlusion on human skin

In order to investigate the el led of occlusion on the skin, the flexor sides of both upper arms were covered with column-shaped closed chambers, 30 mm in outer diameter. 20 mm in inner diameter. and 5 mm in height, which were made of polyethylene loam. The tops of the chambers were sealed be plastic films with various levels of water vapor permeability to control moisture in each chamber. The raised chamber walls prevented direct contact between the skin and the plastic film. After 24 h of application, morphological changes of the skin surface were observed microscopically by the nitrocellulose-replica method. Although no visual alterations were found on all areas of occluded skin, microscopic evaluation showed that simple occlusion by films induced an increase in the number of deepened skin furrows on the skin surface. This increase was associated with lower water vapor permeability of the films, as well as with higher values of both temperature and humidity on the test day. Thus, since conditions which facilitate perspiration from the skin lend to cause skin irritation, prolonged exposure of the skin to sweat by simple occlusion may act as a primary skin irritant     

Effects of topical petrolatum and salicylic acid upon skin photoreaction to UVA

Various agents which can be used in combination can also interfere with phototherapy. In this study, the effects of topical petrolatum and 20% salicylic acid in petrolatum upon skin photoreaction to UVA were investigated, in an in vivo test. Minimal phototoxic dose (MPD) test was performed on 31 volunteers and the test was repeated with thin (0.1 cc/25 cm(2)) petrolatum, thick (0.3 cc/25 cm(2)) petrolatum, thin 20% salicylic acid in petrolatum, thick 20% salicylic acid in petrolatum and sunscreen. The effect of each agent on MPD was investigated. MPD was increased with thin and thick applications of all agents. Also, MPD was increased with 20% salicylic acid in petrolatum when compared with pure petrolatum, in the same thickness. The application of petrolatum and salicylic acid in petrolatum just before PUVA therapy is not recommended because of their blocking effects.     

Effect of glove occlusion on human skin

Skin harrier function was studied after use of occlusive gloves on normal and compromised skin. 2 studies were performed (Study A and B), and the effects were evaluated by non-invasive methods. Participants in the studies were instructed to wear an occlusive glove on one hand, while the other hand served as control. The gloves used were hypoallergenic, non-latex. Study A: 20 volunteers wore a glove on normal skin 6 h/day for 3 days. Study B: 20 volunteers wore a glove on sodium fauryl sulfa lei S LSI-compromised skin 6 h/day for 3 days. Skin harrier function was evaluated by measurement of transepidermal water loss (TEWL) (Evaporimeter), skin hydration by electrical capacitance (Corneometer) and inflammation was evaluated by erythema index (DermaSpetrometer). Results: Study A. Glove occlusion on normal skin 6 h/day for 3 days caused no significant influence on the water barrier function. Study B: Glove occlusion on SLS-compromised skin for the same period of time had a significantly negative effect on the water barrier function. It is concluded that occlusion may be an additional factor in the pathogenesis of cumulative irritant contact dermatitis.     

Correlations between human skin bacteria and skin lipids

Correlation matrices were constructed for various human skin variables (propionibacteria, micrococcaceae, sebum excretion rate, percentage of free fatty acids and free fatty acid production rate). Two independent populations were studied (n= 87 and n= 103), and a subpopulation (n= 30) was investigated on three occasions at intervals of 1 month. In this way consistently high correlations could be differentiated from ‘fortuitous’ correlations. Propionibacteria versus micrococcaceae showed the highest correlation coefficient and propionibacteria versus percentage free fatty acids was also highly correlated. A scatter diagram indicated a relationship between the lower threshold of microbial density and sebum excretion rate. An explanation based on relative duct and gland size is presented.     

Effects of physical and chemical treatments upon biophysical properties and micro-relief of human skin

The aim of the present study was to determine the attendant effects of physical (tape-stripping) and chemical (three commercial hydrating formulations) treatments upon biophysical and micro-relief properties of human skin. In the first set of experiment, the effects of tape-stripping onto human stratum corneum (SC) biophysical and micro-relief properties were assessed in nine volunteers. Transepidermal water loss (TEWL), skin hydration and micro-relief parameters (including total length of the lines in mm per mm(2); total surface in %; roughness of the skin measured in gray level (Ra); maximum profile valley (Rv) depth; maximum profile peak height (Rp); maximum height (Rt), peak density (Pc) and coefficient of anisotropy) were determined by using SkinEvidence Pro after subsequent tape-stripping of SC. The relevance of roughness determination as gray level by SkinEvidence Pro was confirmed by using surface roughness standards. In the second set of experiment, the effectiveness of three commercial hydrating formulations onto human SC biophysical parameters and micro-relief properties were assessed in six volunteers. TEWL, hydration and micro-relief parameters were assessed onto pre-treated acetone skin and then treated by three commercial hydrating formulations after 2, 4 and 6 h skin exposure. A linear relation between hydration and cutaneous parameters (total length of the lines, Ra and Rp) as function of SC removed was shown. Skin barrier properties evaluated by TEWL measurements, were not modified by topical formulations. However, skin treated by topical formulations showed slightly higher hydration than the one determined in control group, while micro-relief parameters were not modified. In this study was showed that biophysical and micro-relief parameters were closely related in tape-stripping experiment. Efficiency of topical formulations was suggested upon skin hydration but not onto skin micro-relief and barrier function recovering. From both experiments, it appears that different mechanisms relating to skin hydration and potential modification of cutaneous micro-relief were suggested.     

Effect of glove occlusion on the skin barrier

Wet work tasks are the most common exposures leading to occupational irritant contact dermatitis. Use of liquid‐proof gloves is recommended when performing wet work, however, gloves may also contribute to impairment of the skin barrier and development of irritant contact dermatitis. The aim of this study is to review the literature on the effects of glove occlusion on skin barrier function. The PubMed database was searched up to 1 February 2015 for articles on the association between glove occlusion and skin barrier function, including human studies only and in English. Only experimental studies including assessment of the skin barrier function were included in the data analysis. Thirteen articles were identified, 8 with focus on occlusion alone, 7 with focus on occlusion in combination with irritant exposure (some overlapping), and 2 field studies. In conclusion, data from the literature showed that the negative effect of occlusion in itself is limited, and that only extensive and long‐term occlusion will cause barrier impairment. However, studies investigating combined effect of occlusion and exposure to soaps/detergents indicate that occlusion significantly enhances the skin barrier damage caused by detergents/soaps in a dose‐response fashion.     

Sex,constancy, and skin bacteria

Summary Quantitative studies of the aerobic flora of seven skin sites in 16 volunteers were repeated after 3 months. The total aerobic densities of the sites differed, male carried more organisms than females and also more biotypes. Qualitative differences in the flora could be detected.     

Effect of glove occlusion on human skin (II)

Gloves are indispensable in many occupations. Irritant skin reactions from gloves have, however, been reported. In the present study, the effect of long-term glove occlusion on normal skin (6 h/day for 14 days) was studied and, in addition, the effect of a cotton glove worn under the occlusive glove was also studied. 2 studies were performed (studies A and B). Study A: 19 volunteers wore an occlusive glove on normal skin 6 h/day for 14 days. They wore the glove on one hand only, while the other hand served as control. Study B: 18 volunteers wore occlusive gloves on both hands on normal skin. A cotton glove was worn under the occlusive glove on either the left or the right hand. Skin barrier function was evaluated by measurement of transepidermal water loss (TEWL) (Evaporimeter) skin hydration by electrical capacitance (Corneometer) and inflammation by erythema index (Derma-Spectrometer). The gloves used were hypoallergenic non-latex gloves. Results Study A: glove occlusion on normal skin 6 h/day for 14 days had a significant negative effect on skin barrier function, as measured by TEWL. Study B: the negative effect on skin barrier function from occlusive gloves was prevented by the use of a cotton glove. It is concluded that gloves may be a substantial factor in the pathogenesis of cumulative irritant contact dermatitis, and that recommendations as to their use are important.     

Lipid uptake and skin occlusion following topical application of oils on adult and infant skin

BACKGROUND: Topical application of oils and oil-based formulations is common practice in skin care for both adults and infants. Only limited knowledge however is available regarding skin penetration and occlusive potential of oils and common methods for measuring skin moisturization fall short when it comes to the moisturizing effect of oils. OBJECTIVE: In this study we used in vivo confocal Raman microspectroscopy to test the efficacy of paraffin oil (mineral oil) and two vegetable oils in terms of skin penetration and occlusion. Petrolatum was used as a positive control. METHODS: The products were applied topically on the forearms of nine volunteers and seven infants and Raman spectra were acquired before and at 30 and 90 min following application. Depth concentration profiles for lipid and water were calculated from the Raman spectra. Skin occlusion was assessed from the amount of stratum corneum (SC) swelling measured from the water concentration profiles. RESULTS: The paraffin oil and the vegetable oils penetrate the top layers of the SC with similar concentration profiles, a result that was confirmed both for adult and infant skin. The three oils tested demonstrated modest SC swelling (10-20%) compared to moderate swelling (40-60%) for petrolatum. CONCLUSION: These data indicate that there is no statistical difference between the paraffin oil and vegetable oils in terms of skin penetration and skin occlusion. The results for petrolatum show that in vivo confocal Raman microspectroscopy is sensitive and specific enough to measure both lipid uptake and skin occlusion events following topical application.     

Physiological skin surface water loss dynamics of human vulvar and forearm skin

In order to estimate the influence of occlusion and sweating on forearm and vulvar skin surface water loss (SSWL), both were measured simultaneously and continuously for 30 min in 8 healthy women. Vulvar SSWL decreased significantly during the measuring period from 24.9 +/- 5.2 gm-2 h-1 (mean +/- standard error of the mean) in the first 5 min, to 13.4 +/- 1.7 gm-2 h-1 in the last 5 min (p less than 0.05), whereas no significant changes were observed in forearm SSWL. The vulvar SSWL decay curve followed a logarithmic equation of the form y = a*tb. Irregular SSWL increases ('bursts') were observed in vulvar (but not in forearm) skin of 7 out of 8 women. These SSWL bursts were considered to be caused by sweating. The study shows possible causes of systematic errors in vulvar irritation studies. Methods for error reduction are discussed.     

Quantitation of skin bacteria: lethality of the wash solution used to remove bacteria.

A widely used technique for the quantitative removal of bacteria from the skin uses a detergent, Triton X-100 (p, t-octylphenoxynonaethoxyethanol), to remove and suspend the bacteria. We determined the half-life for the survival of five common skin bacteria suspended in the solution. The shortest-lived was Streptococcus pyogenes with a half-life of 0.9 hours. All of the others (Propionibacterium acnes, Staphylococcus epidermidis, Staphylococcus aureus, and Klebsiella pneumoniae) had half-lives of 1.5 hours or longer. K. pneumoniae, the only Gram-negative species tested, had a half-life of more than 30 hours. Thus, a one hour delay in plating and incubation of samples suspended in this detergent solution inhibits quantitation of most species tested.     

Sensitive skin evaluation in the Japanese population

Sensitive skin syndrome was first described in 1977; however, no robust study has been carried out to evaluate its prevalence in Japan. A national representative sample of the Japanese population over the age of 18 years was taken. Individuals were questioned by telephone and selected according to the quota method. When asked “Do you have a sensitive skin?”, 52.84% of men and 55.98% of women answered “rather sensitive” or “very sensitive”. There was no significant difference (P = 0.22) between the two sexes. The non‐response rate among respondents was zero, suggesting that the term “sensitive skin” held a meaning for the majority of the population. Concerning questions about the onset of a rash, tingling or irritation in the presence of various factors, such as emotional issues, cold, heat, sun, dry air, air‐conditioning, water, air pollution and temperature variations, respondents with rather sensitive or very sensitive skin responded “yes” more often than others: approximately three‐times more often for water (18.97%/6.15%), air pollution (39.29%/12.45%) and warm climatic conditions (29.74%/9.8%). To our knowledge, this epidemiological study is the first to focus on sensitive skin among Japanese people of this century. It is of particular interest for two reasons: (i) it was conducted on a representative sample of the Japanese population; and (ii) the methodology used was identical to that used for sensitive skin assessment studies conducted in Europe and the USA, making it possible to draw certain comparisons.     

Relevance of skin phototyping to a Korean population

We have determined skin phototype by a self-reporting questionnaire proposed by Fitzpatrick in 128 Korean medical students. We also measured the minimal erythema dose (MED), minimal melanogenic dose and investigated their relationship to phototype. A questionnaire of skin phototypes revealed that 13.3% of the students are skin phototypes I and II. Based on MEDs, we demonstrated that 14.8% of the students fall into the UV-sensitive group as defined by an MED of less than 40 mJ/cm² which is the upper range of MED of phototypes I and II in a white population. The skin phototypes did not show a positive correlation to MEDs and only 2.3% of students classified as skin phototypes I and II showed an MED below 40mJ/cm². This study indicates that the skin phototyping method proposed by Fitzpatrick does not reliably predict UV-sensitive individuals within the Korean population.     

The effect of population diversity on skin irritation

The impact of many human variables on the response to skin irritating substances has been studied to varying degrees, including the impact of age, sex, and atopic status. However, the importance of ethnic origin has been more difficult to investigate, leading to a relative paucity of compelling data, either for or against the existence of differences. A primary reason for this lack is that studies on different ethnic groups often have to be undertaken in different locations thus introducing variables, e.g. time, environmental conditions that confound interpretations. In the present work, an attempt has been made to eliminate all variables except ethnicity by conducting a study on 2 distinct populations (Punjabis and Tamils) at the same location on the same day with a single assessor of the skin reactions, using sodium lauryl sulfate as the skin irritant. The skin reactions were assessed visually, and it was demonstrated that the modality of the reactions in these 2 populations had clear differences, but that the dose-response profiles were very similar. Thus, although the irritant response was expressed differently (e.g. erythema was much less evident in the darker Tamil population), the overall outcome was that the populations reacted in an equivalent manner.