Skin temperature of UV-induced erythema correlated to laser Doppler flowmetry and skin reflectance measured redness

Background/aims: The sensitivity of human skin to UV radiation is investigated by visual grading of the resulting erythema reactions 24 h after exposure to a series of increasing UV doses. Visual erythema assessment is, however, subjective and depends on pigmentation and redness of the adjacent un-irradiated skin and can be aided by skin reflectance spectroscopy and laser Doppler blood flow measurements. Erythema is accompanied by a raised skin temperature, and this reaction might be utilised as a simple objective measurement of UV sensitivity. Methods: Sixteen patients with cutaneous malignant melanoma, 16 patients with basal cell carcinoma, and 36 healthy people were phototested with simulated sunlight on previously UV un-exposed buttock skin. The resulting erythema reactions were graded visually 20-24 h post-exposure and measured by skin reflectance spectroscopy and laser Doppler flowmetry, and the surface skin temperature was determined in the erythema reactions and in adjacent un-irradiated skin by a contact thermometer. Results: Skin surface temperature in UV-induced erythema reactions was dose dependent, was statistically identical in skin cancer patients and in healthy people, and was age independent. The average temperature increase in barely perceptible erythema was 0.7°C (SD=1.1°C), and in bright red erythema it was 3.5°C (SD=2.0°C). Skin surface temperature increases were correlated to measurements by skin reflectance spectroscopy and by laser Doppler flowmetry. Conclusions: Skin surface temperature changes can be used as a simple objective measurement of UV sensitivity in healthy people and in skin cancer patients and may be particularly useful in heavily pigmented people where visual assessment of erythema is difficult or impossible.     

Threshold level for measurement of UV sensitivity: reproducibility of phototest

The ultraviolet (UV) sensitivity is determined by a phototest where the skin is exposed to well-defined doses of UV radiation and the resulting erythema is graded by visual scoring after 20–24 h. In this study we wanted to estimate the reproducibility of erythema assessment in phototesting. Twenty-one healthy Caucasians with skin types I to IV were phototested on UV un-exposed buttock skin using a xenon lamp solar simulator. Twenty-four hours after UV exposure eight physicians independently graded the erythema reactions two times. Data were analysed using inter-and intra-observer agreement and kappa statistics, which adjusts for agreement that could be caused by chance alone. Observed agreement and kappa statistics were found to decrease with increasing intensity of erythema and to be lower for skin types III and IV compared to skin types I and II. Intra-observer agreement was uniformly better than inter-observer agreement. The difference between observers assessment could be as much as three clinical erythema grades. Physicians's previous experience with phototesting only had a minor influence on agreement. In conclusion, phototesting is based on subjective assessment of erythema and is not as precise and reproducible as expected. Agreement was better for barely perceptible erythema than for erythema with a well-defined border and we therefore recommend that the barely perceptible erythema reaction should be used for measurement of the minimal erythema dose.     

Minimal erythema dose in UV-shielded and UV-exposed skin predicted by skin reflectance measured pigmentation

Aims: To investigate the relationships between epidermal thickness, age, skin pigmentation and UV sensitivity in sun-exposed skin and skin not exposed to the sun in healthy people without skin cancer or skin diseases. Methods: Phototesting with a xenon arc solar simulator was performed in 137 healthy Caucasians in buttock skin un-exposed to UV (27 children, 34 young adults and 32 older adults) and in skin of the back exposed to UV (44 young adults). The pigmentation of the phototest sites was measured objectively by a skin reflectance spectrometer before phototesting. Thickness of the stratum corneum and the cellular epidermis were measured in skin biopsies from the phototest sites. All measurements were performed in the winter and spring months. Results: Stratum corneum and cellular epidermis were thinner at the back than at the buttocks (P<0.01). Thickness of the stratum corneum at the back or the buttocks was not related to the degree of skin pigmentation (P=0.62 and P=0.20, respectively). Thickness of the stratum corneum at the buttocks was unaffected by gender (P=0.42) and age (P=0.83) whereas cellular epidermis decreased with age (P<0.01) and was thinner in females than in males (P<0.01). In spite of the higher pigmentation at the back than at the buttocks, the minimal erythema dose (MED) was lower at the back than at the buttocks (x=2.7 and x=2.2 SED's, respectively; P=0.04). Given the same degree of skin pigmentation, there was no difference in the MED in buttock skin in children, young adults and older adults un-exposed to UV (P= 0.61). Prediction of the MED in un-exposed buttock skin and in exposed skin of the back by a theoretical model based on an exponential function of the measured skin pigmentation was found to provide good estimates of the MED determined by phototest. Conclusion: Skin pigmentation at un-exposed buttock skin can reliably predict the constitutive UV sensitivity in healthy Caucasian children and adults and is recommended in surveys where phototesting cannot be performed.     

The Relationship among Minimal Erythema Dose,Minimal Delayed Tanning Dose,and Skin Color

The relationship among minimal erythema dose (MED), minimal delayed tanning dose (MDTD), and skin color was examined in 16 healthy volunteers using three different spectra. The subjects were exposed to UVB, UVA+B, and UV+Visible light (UV+Visible) with a xenon arc solar simulator as a light source. The MEDs for UVB and UVA+B were less than the MDTDs, whereas the MED for UV+Visible was higher than the MDTD. There was no significant correlation between the MED and the MDTD for UVB or UVA+B. The MED for UV+Visible was significantly correlated to the MDTD (p<0.01). Skin color significantly correlated with MEDs for UVB and UVA+B (p<0.01), but not for UV+Visible. There was no significant correlation between skin color and the MDTD for any spectra. From these results, it is suggested that the relationship between erythemal and melanogenic responses is dependent on spectral bands of the light source and that skin color is a predictor of UV-induced erythema.     

The Relationship of Sun Protection Factor to Minimal Erythema Dose,Japanese Skin Type,and Skin Color

The relationship of sun protection factor (SPF) to minimal erythema dose (MED), Japanese skin type, and skin color was investigated on the unexposed backs of 48 healthy subjects. SPF of a UVB-sunscreen was determined using sun lamps as a light source. A significant correlation was found between SPF and MED; subjects with lower MED showed higher SPF. The average SPF decreased with increasing skin type. There was no significant correlation between SPF and skin color (L*a*b* color system).     

UV transmission and UV protection factor (UPF) measured on split skin following exposure to UVB radiation — correlation with the minimal erythema dose (MED)

In this study the ultraviolet (UV) transmission of split skin exposed to UVB radiation and of non-exposed skin was compared in the 280-390 nm wavelength range and quantified. In addition, the correlation between the increase in the minimal erythema dose (MED) associated with a defined exposure to UVB and the ultraviolet protection factor (UPF) calculated from the transmission data was investigated. The study population consisted of 12 patients. Two pieces of split skin of the same thickness (0.3 mm) were taken from the right thigh of each patient. One specimen was removed from an area of non-exposed healthy skin and the other from an area which had been exposed to UVB radiation for a period of 12 days in which the initial dose of 1/3 MED was raised by 1/3 MED every 4 days. The split skin specimens were stretched over a special frame; subsequently, the UV transmission was determined with a spectrophotometer. The mean values obtained for UV transmission were all significantly below the initial data for non-exposed split skin. In the UV range of 280--390 nm, the transmission measured in the exposed specimens was 49.1% of the value measured in the non-exposed split skin (P<0.05). The corresponding values for the UVA range (315--390 nm) and the UVB range (280--315 nm) were 50.1% and 29.5%, respectively (P<0.05), based on the initial transmission data obtained from non-exposed skin. The clinical determination of MED after 12 days of exposure to UVB yielded mean values that were 3.2 times the initial values. Moreover, the mean UPFs calculated from the transmission data measured at the end of the 12-day exposure period were also about three times the initial values. The present study has thus established a significant correlation between the clinical MED values and the UPFs calculated from the transmission data measured following exposure to UVB.     

Epidermal thickness,skin pigmentation and constitutive photosensitivity

The important factors for UV sensitivity in humans are considered to be the skin pigmentation and the epidermal thickness. In this study on 73 Caucasians (age 20–85 years), we investigated in UV unexposed buttock skin the relationship between the UV sensitivity and constitutive skin pigmentation and thickness of the stratum corneum and the cellular part of the epidermis, in 34 normal people and in 39 skin cancer patients (20 patients with cutaneous malignant melanoma and 19 patients with basal cell carcinoma of the skin). Skin pigmentation was measured by skin reflectance spectroscopy, and UV sensitivity by phototest with a solar simulator. Thicknesses of the stratum corneum and the cellular part of the epidermis were determined by light microscopic evaluation of skin biopsies from the phototest areas. We found that epidermal thickness was independent of skin type and was not correlated to constitutive skin pigmentation. Thickness of the stratum corneum was statistically not different in normal persons and in skin cancer patients (P=0.4l) and was independent of gender (P=0.61) and age (P=0.56), while thickness of the cellular epidermis decreased with age (P<0.01). Stratum corneum thickness was found to be of minor importance for the constitutive UV sensitivity (accounting for on average 11% of the total photoprotection), which was mainly determined by the constitutive skin pigmentation (goodness-of-fit for correlation r=0.83). A theoretical model for the relationship of UV dose to induction of clinical erythema grade and skin pigmentation and thickness of the stratum corneum was developed. Objective measurements of skin pigmentation in UV unexposed skin by skin reflectance spectroscopy in Caucasians, normal people and people with cutaneous malignant melanoma and basal cell carcinoma of the skin predicts the constitutive UV sensitivity with a high degree of precision.     

Skin phototyping in a Chinese female population: analysis of four hundred and four cases from four major cities of China

BACKGROUND/PURPOSE: The sun-reactive skin types in 404 Chinese females living in different cities were investigated in this study. METHODS: A questionnaire was designed according to the original concept of skin types proposed by Fitzpatrick and the investigation was conducted in two ways: self-administered reporting and then a personal interview. Minimal erythema dose (MED) and minimal persistent pigmentation dose (MPPD) were also measured in part of the volunteers with a standard solar simulator. RESULTS: The results show that in the way of personal interview, the predominant skin type of the investigated group is type III (71.4%), and then type II (14.7%) and type IV (14.2%), while in the self-reporting manner, the result is as follows: type III, 74.3%, type II, 25.6% and type IV, 1%. There are no skin type I, V or VI in the studied group. MED and MPPD from the same population show some relevance to the skin types, e.g. with the change of skin type from Type II to IV, the mean value of MED increases gradually and the MPPD decreases slightly. CONCLUSIONS: From the study we concluded that the skin types of the investigated Chinese females are principally type III (more than 70%), and then type II and type IV. The different ways of answering the questionnaire did not affect the results remarkably. The measurements of photobiology parameters confirmed that there is a certain correlation between skin types and MED or MPPD determined in this group of volunteers.     

Photosensitivity of murine skin greatly depends on the genetic background: clinically relevant dose as a new measure to replace minimal erythema dose in mouse studies

Artificial UV irradiation of murine skin is a frequently used method for testing photosensitivity, study carcinogenesis and photoprotective effects of different compounds. However, doses of UV radiation and mouse strains used in experiments vary greatly. The genetic background of mice may influence the photosensitivity as melanin content, pigmentation and hair cycle parameters are dissimilar. Doses of UV are often expressed in relation to the minimal erythema dose (MED) that was not necessarily determined for the given strain. We set out to standardize the method of measuring photosensitivity in three commonly used mouse strains, C57BL/6N, Balb/c and SKH‐1. We found that MED may not be determined for some strains as erythema development in mice with diverse genotypes differs greatly. We measured the oedema response in vivo and ex vivo by using OCT. Given the strain‐specific variability of erythema, we introduced Clinically Relevant Dose (CRD) as a new term to replace MED in experiments, to describe the lowest dose that triggers a perceptible skin reaction in mice. Not only the CRD but the proportion of erythema and oedema were different in strains examined. C57BL/6N mice display skin reactions at the lowest UVB dose, while SKH‐1 hairless mice show changes, mostly oedema, after higher doses of UVB. The cellular composition and skin thickness were examined by histopathology. IL‐1beta and IL‐6 levels in skin correlated with the increasing doses of UVB. Despite the variations in the degree of erythema and oedema, no major differences in cytokine expressions were seen among various strains of mice.     

Skin pigmentation in Caucasian babies is high and evenly distributed throughout the body

To investigate if Caucasian babies have particular sun sensitive skin and if skin pigmentation before any sun exposure is uniform throughout the body, we measured skin pigmentation objectively by skin reflectance spectroscopy in 10 anatomical sites in 20 healthy Caucasian babies (mean age 5 months, range 1 to 10 months) that had not been sun exposed previously. We found that skin pigmentation at all the measured sites was significantly higher than the constitutive pigmentation in Caucasian adults ( P <0.01). Furthermore, the level of skin pigmentation in all the 10 measured sites in the babies was statistically not different ( P <0.31) and there was no gender differences in pigmentation for any site.     

UV-induced skin changes due to regular use of commercial sunbeds

BACKGROUND/AIM: Increased pigmentation and thickening of the epidermis are the most important photoprotective skin reactions induced by ultraviolet (UV) radiation. The present study was designed to find out what changes are induced by regular use of commercial sunbeds twice weekly over a period of 6 weeks. METHODS: The parameters analysed were skin pigmentation measured by chromametry, minimal erythema dose (MED) as a parameter of light sensitivity, epidermal thickening as determined by histology, induction of keratinocyte apoptosis as determined by TUNEL staining and antioxidant metabolism as measured by changes of cis- and trans-urocanic acid (UCA) content of the skin. RESULTS: As expected, chromametry confirmed the clinically obvious increased skin pigmentation. However, no increase in MED was observed. In addition, neither epidermal thickening nor sunburn cells were seen. Significant detectable changes in proportion of the UCA isomer content of the UV-exposed skin were seen. The total UCA and cis-UCA content increased significantly between nearly all points of measurement. The amount of trans-UCA first decreased, then increased significantly between the different time points. CONCLUSION: Our data indicate that sunbed-induced tanning is non-protective, which has to be addressed for persons looking for this effect before planning a stay in a sunny climate. However, sunbed-induced tanning may influence immunological reactions.     

Skin irritation in man: a comparative bioengineering study using improved reflectance spectroscopy

Variable types of skin irritation were induced in 8 human female volunteers, ranging from subclinical to visible erythema with slight oedema. Skin reactions were graded clinically and objectively using transepidermal water loss (TEWL), laser Doppler flowmetry (LDF) and improved reflectance spectroscopy. This last technique enables separation of in vivo erythemas into relatively deoxygenated (venous-deoxy hem) and oxygenated (arterial oxy hem) haemoglobin components. Compared to uninvolved skin, an empty patch increased oxy hem by 197%± 121%( p < 0.05). Exposure to vehicles also changed skin biophysics. At sodium lauryl sulfate (SLS) and hydrochloric acid (HCL) exposed sites, a linear correlation between concentration and oxy hem. LDF and TEWL was found. These chemicals predominantly increased TEWL values. Nonanoic acid (NON) and imipramine (IMI) also raised oxs hem, LDI and TEWL values linear at increasing concentrations. Although IMI 2.5% clinically was graded as a type ++ response, no significant increase in TEWL was found. The improved reflectance spectroscopic technique proved valid in skin irritation studies, with a higher sensitivity than laser Doppler flowmetry, and allowed irritant vascular reactions to be discriminated into arterial and venous components. Furthermore, our observations clearly demonstrate that clinical indistinguishable skin irritation reactions induce significantly different changes in barrier function (disruption) and vascular status.     

中国城市女性人群皮肤类型调查及相关研究

目的：调查中国女性群体的皮肤光型或日光反应性分型。方法：按照Fitzpatrick分型概念设计问卷,采用引导性答卷和自主性答卷两种方式进行调查;然后利用标准日光模拟器测定受试者的最小红斑量(MED)和最小持续黑化量(MPPD),比较分析这些参数在不同皮肤类型之间的变化。结果：接受调查的404名城市女性在引导性调查和自主性调查中．Ⅲ型皮肤分别占71．1％和74.3％,Ⅱ型分别占14．7％和25．6％,Ⅳ分别占14．2％和1．0％。未见Ⅰ、Ⅴ、Ⅵ型皮肤。上述皮肤类型和所测定的MED值和MPPD值有较好的对应变化关系,即从Ⅱ型到Ⅳ型皮肤,MED值逐渐增加,而MPPD值逐渐减小,在不同皮肤类型之间差异有显著性。结论：在所调查的中国女性人群中皮肤类型以Ⅲ型为主,其次是Ⅱ型和Ⅳ型。皮肤类型和所测的MED、MPPD值有良好的相关性。     

橙皮苷、β-七叶皂苷、丹参酮等局部外用对甲皱皮肤微循环的影响

目的：研究局部外用8种天然植物提取物对皮肤微循环的影响。方法：给受试者中指甲皱处分别涂1％植物提取物,并安放激光多普勒检测探头,稳定5min后开始记录甲皱皮肤血流灌注量,以后每5min记录1次,每次1min,共观察30min取平均值。基质作对照。对有效成分进一步观察浓度为0．10％、0．01％药物对皮肤血液灌注量的影响,并用毛细血管微循环仪观察其对红细胞血流速度的影响。结果：1．00％、0．10％橙皮苷可以显著增加皮肤的血液灌注量,外用0．10％橙皮苷亦可使红细胞的血流速度显著增加。结论：橙皮苷局部外用可以改善皮肤的微循环。     

广州地区102例正常人紫外线最小红斑量测定

目的:测定广州地区正常人紫外线最小红斑量(MED)的正常值范围,探讨其与性别、年龄、皮肤日光类型的关系。方法:以SUV1000型日光紫外模拟器作为照射光源,测定102名健康志愿者腹部正常皮肤的MED值(Ⅲ型、Ⅳ型皮肤)。结果:102名受试者MED均值:UVA为50.0 J/cm2,UVB为43.0 m J/cm2。不同皮肤类型间,Ⅲ型皮肤MED均值:UVA为38.5 J/cm2,UVB为36.1 m J/cm2;Ⅳ型皮肤MED均值:UVA为50.0 J/cm2,UVB为47.0 m J/cm2,Ⅳ皮肤MED均值均明显大于Ⅲ型皮肤(P值均<0.01)。不同性别间,男性MED均值:UVA为50.0 J/cm2,UVB为43.0 m J/cm2;女性:UVA为50.0 J/cm2,UVB为43.0 m J/cm2,不同性别间差异均无统计学意义(P值均>0.05)。不同性别的不同年龄阶段间UVA、UVB MED均值差异均无统计学意义(P值均>0.05);UVA-MED的正常值范围为≥30 J/cm2,UVBMED的正常值范围为≥29.1 m J/cm2。结论:紫外线MED的影响因素与皮肤日光反应类型有关,Ⅲ型皮肤UVA-MED、UVB-MED均明显低于Ⅳ型皮肤(P<0.01)。本组受试者MED与性别和年龄无直接关系。     

Erythema and melanogenesis action spectra in heavily pigmented individuals as compared to fair-skinned Caucasians

The protective role of epidermal melanin pigmentation against chronic exposure to ultraviolet radiation is widely accepted, although its photoprotective effect against acute exposure is less certain. In this study, the action spectra of erythema and melanogenesis in heavily pigmented individuals (skin type V) were determined at 295, 305, 315, and 365 nm, and compared with those of skin types I and II. When the erythema and melanogenesis action spectra for skin type V were normalized to 295 nm, they were identical to the corresponding action spectra for fair-skinned individuals, indicating that the photoprotection of epidermal melanin pigmentation is essentially independent of wavelength. The ratio of values for the minimum erythema dose (MED) between skin type V and skin types I and II was 2.29, which is close to the ratio of pigment in these skin types, as measured by diffuse reflectance spectroscopy in the visible range. The minimum immediate pigment darkening dose (IPD) and the minimum melanogenic dose (MMD) at 365 nm, and the MED and MMD at 315 nm were the same for all skin types, while the variation of MED for every skin type was maximum at 305 and 365 nm. The results provide circumstantial evidence that erythema and melanogenesis have the same mechanism at short-wavelength UVB (295 and 305 nm), and different mechanisms in UVA (365 nm). Furthermore, the 24 h MED at 305 nm appears to be a sensitive indicator of skin type.