Byung Ho Oh

The relation between the amount of sunscreen applied and the sun protection factor in Asian skin

BACKGROUND The measurement of the sun protection factor (SPF) is the usual method in the examination of the effectiveness of sunscreen. The declared SPF is based on the use of a sunscreen layer of 2 mg/cm(2). However, only around a quarter (0.5 mg/cm(2)) of this amount is generally used in real life. Theoretical calculations have suggested that the effectiveness of SPF is related to sunscreen quantity in an exponential way but this was not confirmed in Asian skin. OBJECTIVES This study was performed to investigate the change in SPF values when less than the recommended amount of sunscreen was applied. METHODS A board divided into 10 areas measuring 7 x 4 cm was placed on the back of 15 healthy volunteers. Low- and high-SPF standard reference sunscreens, and two types of sunscreen (SPF 30 and 35) were each applied on 4 areas, 0.5, 1.0, 1.5, and 2.0 mg/cm(2), respectively, and were left to dry for 20 minutes. The irradiation was conducted at a distance of 50 cm using a template (1 x 1 cm) placed directly on the skin with 10 windows allowing ultraviolet (UV) radiation to pass through with a dose increment of 20%. Erythema was evaluated 20 to 24 hours after exposure to UV radiation. RESULTS Sunscreen showed its expected SPF value when 2.0 mg/cm(2) was applied. The SPF values of the different amounts were significantly different from each other and decreased when less was applied (P < .05). The relation between the amount of sunscreen applied and the SPF provided was most likely to follow exponential growth. LIMITATIONS Spectral differences between our solar simulator and the UV sources of commercial laboratories are likely to be important. In addition, differences in sunscreen application techniques may have influenced the ultimate SPF values. CONCLUSIONS This study concludes that to get the expected SPF value, it is important to apply the UV protective sunscreen precisely in the amount of 2.0 mg/cm(2) on Asian skin as recommended by the Food and Drug Administration. In addition, it was difficult to predict the SPF values when the usual amount of 0.5 mg/cm(2) was applied.

The Investigation on the Distribution of Malassezia Yeasts on the Normal Korean Skin by 26S rDNA PCR-RFLP

BACKGROUND Malassezia yeasts are normal flora of the skin that are discovered in 75~98% of health subjects, but since its association with various skin disorders have been known, many studies have been conducted in the distribution of the yeasts. OBJECTIVE To isolate, identify, and classify Malassezia yeasts from the normal human skin of Koreans by using the rapid and accurate molecular biology method (26S rDNA PCR-RFLP) which overcome the limits of morphological and biochemical methods, and to gather a basic database that will show its relation to various skin diseases. METHODS Malassezia yeasts were cultured from clinically healthy human skin using scrub-wash technique at five sites (forehead, cheek, chest, upper arm, and thigh) and swabbing technique at scalp in 160 participants comprised of 80 males and 80 females aged from 0 to 80. Identification of obtained strains were placed into the one of the 11 species by 26S rDNA PCR-RFLP. RESULTS An overall positive culture rate was 62.4% (599/960). As shown in the experiment groups by their age, the positive culture rate was the highest (74.2%) in the age 21~30 and 31~40 (89/120). In the experiment groups by different body areas, the scalp showed the highest positive culture rate of 90% (144/160). On analysis of 26S rDNA PCR-RFLP, M. globosa was the most predominant species in the age 0~10 (32.8%), 11~20 (28.9%), 21~30 (32.3%). M. restricta was identified as predominant species in the age 41~50 (27.9%), 61~70 (31.5%) and 71~80 (24.0%). In the age 31~40 years, M. sympodialis was found to be the most common species (24.6%). According to body site, M. restricta was more frequently recovered in the scalp (56.8%), forehead (39.8%) and cheek (24.0%) and while M. globosa was more frequently recovered in the chest (36.8%). Higher positive culture rates of Malassezia yeasts were shown in male subjects than female counterparts in all body areas except scalp (p<0.05). Especially in this study, M. dermatis, newly isolated Malassezia species from atopic dermatitis patient in Japan, was isolated and identified in 19 cases (1.9%) in healthy subjects. CONCLUSION The key is to recognize the existence of a difference in the type of Malassezia species in different ages as well as body areas, which reflects differing skin lipid levels in various ages and different body areas. Moreover, 26S rDNA PCR-RFLP analysis which was opted in this study could provide a sensitive and rapid identification system for Malassezia species, which may be applied to epidemiological surveys and clinical practice.

Comparison of Nested PCR and RFLP for Identification and Classification of Malassezia Yeasts from Healthy Human Skin

BACKGROUND Malassezia yeasts are normal flora of the skin found in 75~98% of healthy subjects. The accurate identification of the Malassezia species is important for determining the pathogenesis of the Malassezia yeasts with regard to various skin diseases such as Malassezia folliculitis, seborrheic dermatitis, and atopic dermatitis. OBJECTIVE This research was conducted to determine a more accurate and rapid molecular test for the identification and classification of Malassezia yeasts. METHODS We compared the accuracy and efficacy of restriction fragment length polymorphism (RFLP) and the nested polymerase chain reaction (PCR) for the identification of Malassezia yeasts. RESULTS Although both methods demonstrated rapid and reliable results with regard to identification, the nested PCR method was faster. However, 7 different Malassezia species (1.2%) were identified by the nested PCR compared to the RFLP method. CONCLUSION Our results show that RFLP method was relatively more accurate and reliable for the detection of various Malassezia species compared to the nested PCR. But, in the aspect of simplicity and time saving, the latter method has its own advantages. In addition, the 26S rDNA, which was targeted in this study, contains highly conserved base sequences and enough sequence variation for inter-species identification of Malassezia yeasts.

Epidemiologic Study of Malassezia Yeasts in Seborrheic Dermatitis Patients by the Analysis of 26S rDNA PCR-RFLP

BACKGROUND This case-control study concerns a molecular biological method based on the data gathered from a group of Korean subjects to examine the distribution of Malassezia yeasts in seborrheic dermatitis (SD) patients. Cultures for Malassezia yeasts were taken from the foreheads, cheeks and chests of 60 patients with SD and in 60 healthy controls of equivalent age. OBJECTIVE The purpose of this study is to identify the relationship between certain species of Malassezia and SD. This was done by analyzing the differences in the distribution of Malassezia species in terms of age and body parts of the host with healthy controls. METHODS 26S rDNA PCR-RFLP, a fast and accurate molecular biological method, was used to overcome the limits of morphological and biochemical methods. RESULTS The positive Malassezia culture rate was 51.7% in patients with SD, which was lower than that of healthy adults (63.9%). M. restricta was dominant in patients with SD (19.5%). Likewise, M. restricta was identified as a common species (20.5%) in healthy controls. In the ages 31~40, M. restricta was found to be the most common species (31.6%) among SD patients. CONCLUSION According to the results of the study, the most frequently isolated species was M. restricta (19.5%) in patients with SD. There was no statistically significant difference in the distribution of Malassezia species between the SD patients and healthy control groups.

Skin Characteristics after Fractional Photothermolysis

Background Fractional photothermolysis makes thousands of minute areas called microthermal treatment zones on the skin surface and transmits thermal injury to facilitate heat shock protein formation around the dermis. Potential side effects include acneiform eruption, herpes simplex virus outbreak, erythema, and post-inflammatory hyperpigmentation. Objective To investigate and compare the changes in the skin of Asian patients after two different fractional photothermolysis systems (FPS) on a split face. Methods A half-split face study was performed with 10,600 nm carbon dioxide FPS on the left and 1,550 nm erbium-doped FPS on the right side of the face. Only one session of laser irradiation and several biophysical measurements were done. Results Although both FPS proved to be effective in treating acne scar and wrinkle patients, a slightly higher satisfaction rating was seen with the 10,600 nm FPS treatment. Both types of FPS showed a significant increase in transepidermal water loss which decreased gradually after treatment and returned to pre-treatment level after 1 week. A decreased reviscometer score was sustained for a longer period in wrinkle areas treated with 10,600 nm FPS. Conclusion Even though the changes in skin varied according to different FPS wave-length, adverse outcomes, such as increased erythema and TEWL were entirely subdued within 3 months of treatment.

A Case of Fibroelastolytic Papulosis on the Neck of a Young Man

Fibroelastolytic papulosis of the neck (FEPN) encompasses a spectrum of two disorders that were previously reported as pseudoxanthoma elasticum-like papillary dermal elastolysis (PXE-PDE) and white fibrous papulosis of the neck (WFPN). The clinical presentation of FEPN is asymptomatic to mildly pruritic whitish-yellow papules that may coalesce into cobblestone patterned plaques that resemble pseudoxanthoma elasticum (PXE). The histology is characterized by a decrease or loss of elastic fibers in the papillary dermis and this is sometimes accompanied by a minimal or nodular increase of dermal collagen fibers. We report here on a 28-year-old Korean man with asymptomatic, multiple, skin-colored to slightly yellowish, match-head sized, cobblestone-patterned papules on the neck, and these were histologically consistent with FEPN and the papules showed slightly increased dermal collagen associated with decreased and fragmented elastic fibers, elastin and tropoelastin. The pathogenesis of FEPN in this case might have been related with mild dermal inflammation, followed by fragmentation, elastolysis and increased dermal collagen.

Isolation of 19 strains of Malassezia dermatis from healthy human skin in Korea

This research was conducted on the cultured samples of 160 healthy men and women aged 0–80 years without any skin disease. Nineteen clinical isolates of Malassezia dermatis showed positive in a catalase test and all grew in 0.5% Tween‐60 and 0.1% Tween‐80 added to 2% glucose/1% peptone culture medium. Round and ellipsoidal yeast cells and budding of the yeast cells were observed by microscopy, resembling Malassezia sympodialis, Malassezia furfur and Malassezia nana. The 26S rDNA polymerase chain reaction restriction fragment length polymorphism (PCR‐RFLP) pattern was the same as for M. dermatis (JCM 11348), the standard strain. 26S rDNA and ITS1 sequencing were performed for exact identification, showing 99% accordance with M. dermatis (AB070361), M. dermatis (AB070356), confirming the species to be new and first to be reported in Korea. Taking a molecular biological classification approach by analyzing the 26S rDNA PCR‐RFLP patterns, we have successfully isolated 19 cases of M. dermatis– the first in Korea.

Low-dose Ultraviolet A1 Phototherapy for Treating Pityriasis Rosea

BACKGROUND UVA1 phototherapy has recently demonstrated high levels of efficacy and tolerability for treating a variety of inflammatory and neoplastic skin diseases. OBJECTIVE The purpose of the present study was to assess the clinical efficacy of UVA1 (340~400 nm) phototherapy for treating pityriasis rosea and to assess the course of the disease after treatment. METHODS Fifteen patients with extensive pityriasis rosea were treated with low-dose UVA1 phototherapy (starting at 10~20 J/cm(2) and then it was increased to 30 J/cm(2)). The treatments were given 2~3 times a week until complete clearance of lesions was achieved or until there was partial improvement without further amelioration, in spite of 5 additional treatments. The rate of clearing was monitored by estimating the pityriasis rosea severity (PRSS) score and the pruritus score. RESULTS The extent of disease (PRSS) in all 15 patients lessened during the study (30.1+/-3.6 vs. 2.0+/-1.6, respectively, p<0.05). The overall reduction of the PRSS showed a significant improvement after the second or third treatment. The pruritus of 12 of 15 patients lessened during the treatment period, and it was unchanged in the remaining 3 patients. The mean previous duration of disease was 11.2+/-4.9 days and this did not interfere with the successful outcome of UVA1 phototherapy. CONCLUSION This study shows that UVA1 phototherapy is a useful, well-tolerated treatment option for patients suffering from pityriasis rosea with extensive eruptions and considerable pruritus.