Evaluation of sunscreen products using a reconstructed skin model exposed to simulated daily ultraviolet radiation: relevance of filtration profile and SPF value for daily photoprotection

Background: The recent definition of a standard daily ultraviolet radiation (DUVR) has allowed us to reproduce non‐zenithal sun exposure conditions. Exposure to simulated DUVR induces biological damage in human skin, suggesting the need for an appropriate photoprotection. Methods: Sunscreen products were evaluated using human reconstructed skin in vitro. Two commercial sunscreens (A and B) having similar sun (burn) protection factor (SPF) values (～15) but different profiles of transmission over the UVA range were tested on skin models exposed to increasing doses of DUVR. Another pair of sunscreens was also tested. One (product C) had an SPF ～18 with a well‐balanced UVB–UVA profile and the other (product D) an SPF of ～27 with low UVA absorption. Biological parameters were assessed by (i) histology, (ii) vimentin immunostaining for dermal fibroblasts, and (iii) analysis of matrix metalloprotease (MMP)‐1 secretion. Results: Products A and C gave better protection from DUVR with regard to fibroblast alterations and MMP‐1 release compared with products B and D, respectively. Conclusion: To ensure an efficient daily photoprotection from DUVR, the filtration profile of the product should be well balanced with a sufficient level of UVA absorption. With regard to end points evaluated in this study, our data suggest that a higher SPF value does not compensate for low UVA filtration.     

Eruptive papules during efalizumab (anti-CD11a) therapy of psoriasis vulgaris: a case series

Background

Sunscreens are being widely used to reduce exposure to harmful ultraviolet (UV) radiation. The fact that some sunscreens are photounstable has been known for many years. Since the UV-absorbing ingredients of sunscreens may be photounstable, especially in the long wavelength region, it is of great interest to determine their degradation during exposure to UV radiation. Our aim was to investigate the photostability of seven commercial sunscreen products after natural UV exposure (UVnat) and artificial UV exposure (UVart).

Methods

Seven commercial sunscreens were studied with absorption spectroscopy. Sunscreen product, 0.5 mg/cm², was placed between plates of silica. The area under the curve (AUC) in the spectrum was calculated for UVA (320–400 nm), UVA1 (340–400 nm), UVA2 (320–340 nm) and UVB (290–320 nm) before (AUC_before) and after (AUC_after) UVart (980 kJ/m² UVA and 12 kJ/m² of UVB) and before and after UVnat. If theAUC Index (AUCI), defined as AUCI = AUC_after/AUC_before, was > 0.80, the sunscreen was considered photostable.

Results

Three sunscreens were unstable after 90 min of UVnat; in the UVA range the AUCI was between 0.41 and 0.76. In the UVB range one of these sunscreens was unstable with an AUCI of 0.75 after 90 min. Three sunscreens were photostable after 120 min of UVnat; in the UVA range the AUCI was between 0.85 and 0.99 and in the UVB range between 0.92 and 1.0. One sunscreen showed in the UVA range an AUCI of 0.87 after UVnat but an AUCI of 0.72 after UVart. Five of the sunscreens were stable in the UVB region.

Conclusion

The present study shows that several sunscreens are photounstable in the UVA range after UVnat and UVart. There is a need for a standardized method to measure photostability, and the photostability should be marked on the sunscreen product.     

Change of ultraviolet absorbance of sunscreens by exposure to solar-simulated radiation

Regarding the outdoor behavior of the Caucasian population, modern sunscreens should provide high and broad-spectrum ultraviolet protection in the ultraviolet B as well as in the ultraviolet A range and should be photochemically stable for ultraviolet doses, which can be expected in solar radiation. At present an assessment of the photostability of suncare products is not a general requirement before marketing. In order to evaluate the photostability of suncare products we conducted an in vitro test and measured the spectral absorbance of 16 sunscreens before, and after exposure to increasing biologically weighted standard erythema doses (5, 12.5, 25, 50) of solar-simulated radiation. Seven of 16 suncare products showed a significant dose- and wavelength-dependent decrease of the ultraviolet A protective capacity, whereas the ability to absorb ultraviolet B was not affected. In the ultraviolet A range, the decrease of absorbance (photoinactivation), respectively, the increase of transmission was 12-48% for an ultraviolet exposure of 25 standard erythema dose. Photoinactivation started in the wavelength range between 320 and 335 nm with a maximum above 350 nm. Furthermore, our analysis showed that the behavior of suncare products was not predictable from its individual ingredients. Neither complex combinations of organic filters nor addition of inorganic filters could absolutely prevent photoinactivation. The inclusion of a single photounstable filter did not mean photoinstability of the complete suncare product. Photoinactivation of sunscreens appears to be an underestimated hazard to the skin, first, by formation of free radicals, second, by increased ultraviolet A transmission.     

In vivo measurement of the photostability of sunscreen products using diffuse reflectance spectroscopy

BACKGROUND/AIM: The issue of the photostability of sunscreens has been frequently raised because of the possible loss of photoprotection, mainly in the UVA range, during sun exposure. Up to now, in vitro techniques have been mainly proposed to evaluate photostability. These techniques have generated controversial debates concerning the predictive value of these in vitro observations in relation to the in vivo reality during sun exposure. METHODS: Diffuse reflectance spectroscopy (DRS) is a recently developed technique that allows measurement of the UVA efficacy of sunscreen products in vivo on human volunteers. The absorption spectrum of the product is obtained by measuring the change in reflection of the skin with and without product. From this absorption spectrum, the UVA protective efficacy of the test product can be calculated for an appropriate source and a given biological action spectrum. We have used the DRS technique in vivo to determine the photostability of sunscreen products by measuring reflection spectra in the UVA range (320-400 nm) before and after product application and before and after UV exposure of the test products. Comparison between these spectra or between the corresponding calculated UVA protection factors has made it possible to determine the remaining level of protection in the UVA range after exposure. This study was designed to compare in vivo the protective efficiency and the photostability of three marketed sunscreen products (SPF 23-30) after solar-simulated exposure for SPF testing or after actual sun exposure. These in vivo data were then compared to in vitro photoinstability results. RESULTS: According to the in vitro measurements, one sunscreen product was found photostable and two products photo-unstable. After UVe exposure for in vivo SPF determination, a decrease in UVA absorption and UVA-PF was observed for the two photo-unstable products, while the photostable product did not present any decrease in UVA absorption. These results were confirmed through exposure to actual sun. CONCLUSION: Our study confirms the prediction of the in vitro methods previously used to assess the photostability of sunscreen products. In addition, DRS provides a powerful new tool for the in vivo simultaneous evaluation of photostability and estimation of the UVA protection factor of sunscreen products performed during the test for SPF determination.     

Effects of UVA radiation on an established immune response in humans and sunscreen efficacy

Abstract: It is well established that ultraviolet radiation has immunomodulatory effects which may be involved in skin cancer. Recent studies have shown that UVA radiation (320–400 nm) as well as UVB (290–320 nm) is immunosuppressive. This means that sunscreens which mainly absorb UVB (protection against erythema) may be less effective in preventing UVR-induced immunosuppression than broad-spectrum products. We have studied the effects of UVA exposure on the human delayed-type hypersensitivity response (DTH) and compared the efficacy of sunscreens having different levels of UVA protection under both solar-simulated radiation (SSR) chronic exposures or acute exposure and outdoor real-life solar exposure conditions. DTH was assessed using recall antigens. Our studies clearly demonstrate the role of UVA in the induction of photoimmunosuppression together with the need for sunscreen products providing efficient photoprotection throughout the entire UV spectrum. These data suggest that sun protection factor may not be sufficient to predict the ability of sunscreens for protection from UV-induced immune suppression. Determining the level of UVA protection is particularly necessary, because UVA seems to have a relatively low contribution to erythema but is highly involved in immunosuppression.     

Photostability of sunscreen products influences the efficiency of protection with regard to UV-induced genotoxic or photoageing-related endpoints

BACKGROUND: Acute as well as chronic sun exposure induces biologically damaging effects in skin including photoageing and cancer. Ultraviolet (UV)A radiation is involved in this process; it is therefore important that sunscreen products provide efficient and stable protection in this range of wavelengths. OBJECTIVES: This study based on in vitro approaches was performed to demonstrate that photostability is an essential requirement to protect against UVA-induced genetic and dermal alterations. METHODS: The protection afforded by two sunscreen products, differing with regard to their photostability, was studied using biological markers related to the genotoxic or photoageing impact of UVA or simulated solar UV radiation (UV-SSR). Comet assay was used to assess direct DNA breakage, photo-oxidized purines and lomefloxacin-induced DNA breaks in nuclei of normal human keratinocytes in culture. In similar conditions, detection of p53 accumulation was performed. The use of reconstructed skin in vitro allowed us to use a three-dimensional model to analyse the dermal and epidermal damage induced by UVA or UV-SSR exposure. Abnormal morphological features of the tissue as well as fibroblast alterations and matrix metalloproteinase-1 release induced by UV exposure have been studied after topical application of products on the skin surface. RESULTS: The results showed that the photostable product afforded better protection with regard to all the criteria studied, compared with the photounstable product. CONCLUSIONS: These data demonstrate that the loss of absorbing efficiency within the UVA wavelength domain due to photoinstability may have detrimental consequences on cell function and lead to impairments that have been implicated in genotoxic events as well as in the photoageing process.     

Cumulative UV radiation dose and outcome in clinical practice: effectiveness of trioxsalen bath PUVA with minimal UVA exposure

BACKGROUND: The cumulative artificial ultraviolet (UV) exposure dose of dermatological patients was prospectively monitored in clinical conditions for a total of 2 years (August 1997 - July 1999). We focused on whole body UV treatments, i.e. the trioxsalen (TMP) bath PUVA, the broad-band UVB, and the UVA plus UVB phototherapy. METHODS: Irradiance of the UV devices was calibrated with a spectroradiometer. The cumulative UV doses received by the patients were recorded. A visual analog scale scoring system (VAS) was employed to assess the improvement of various skin conditions at the end of the treatment course. RESULTS: The analysis included 265 patients (141 females and 124 males) and a total of 311 UV treatment courses. Treatments consisted of 86 courses of TMP bath PUVA for psoriasis with a mean cumulative UVA dose of 3.54 J/cm2 and an improvement rate of 89%. For other conditions, 30 courses were needed, with a cumulative UVA dose of 1.47 J/cm2 and an improvement rate of 76%. Altogether, 47 UVB courses were undertaken for psoriasis, and the mean cumulative unweighted UV dose was 2.20 J/cm2, equivalent to 85 standard erythema doses (SED), and an improvement rate of 85%. A total of 25 UVB courses was used for other skin conditions with a mean UV dose of 1.05 J/ cm2, equivalent to 40 SED, and an improvement rate of 71%. A total of 123 courses of UVA plus UVB phototherapy were completed, resulting in a mean cumulative dose of 73.01 J/cm2 for UVA and 0.75 J/cm2 for the unweighted UVB, equivalent to 29 SED. The VAS improvement rate was 85%. CONCLUSION: The exceptionally low mean cumulative UVA dose in the TMP bath PUVA, taken together with the previous report showing no increase in the risk of squamous cell carcinoma or cutaneous malignant melanoma after TMP bath PUVA, suggests that TMP bath PUVA is an effective and safe therapeutic option.     

UV transmission measurements of small skin specimens with special quartz cuvettes

BACKGROUND: The penetration of different wavelengths of UV radiation through human skin is of major importance, especially for the determination of photoprotective properties of sunscreens and UV-protective clothes. OBJECTIVE: In this study we present a new method for the measurement of UV transmission through small skin specimens. METHODS: The transmission measurements were performed by using a UV spectrophotometer with an integrating sphere operating in the wavelength range of 280-390 nm. For the skin samples, special quartz glass cuvettes were developed which allowed measurements for very thin and small skin specimens. Furthermore, the cuvettes prevented dehydration of the specimens and guaranteed, by using an additional diaphragm, that the transmission data were derived solely from the small skin specimen examined. Specimens measuring 8 x 3 mm(2) with a thickness of 0.3 mm (histometric and sonographic control) were taken from the thighs of 10 subjects via shave biopsy. RESULTS: In the UVA range (315-390 nm) we obtained a mean transmission of 4.6% and for the UVB range (280-315 nm) of 0.9%. No significant (p >0.14) difference of UV transmission was found between the individual skin specimens. CONCLUSION: This new method seems to be well suitable for UV transmission measurements of small skin specimens. As UVA radiation has a much deeper penetration depth and in in vivo situations dermal hemoglobin could have an effect on UV penetration, the present method is better suitable for the investigation of UVB-induced biological adaptation mechanisms and the impact of topical agents on UVB transmission of the epidermis.     

防晒霜的应用和评价

局部应用防晒霜越来越被公众接受。大部分的防晒霜由物理防晒剂和化学防晒剂组成．可以有效地防止紫外线引起的皮肤红斑反应、免疫抑制、光老化以及皮肤癌的发生。防晒霜应有中波紫外线和长波紫外线的全面防护功能。评价防晒霜要从其吸收光谱，衰减系数，中波紫外线防护功能以及长波紫外线防护功能等方面进行考虑。     

The role of glass as a barrier against the transmission of ultraviolet radiation: an experimental study

Background/Purpose: Excessive exposure of the skin to sunlight may cause many symptoms and skin cancer. The aim was to measure the transmission of ultraviolet (UV) A and UVB radiation through glasses of different types, according to the distance from the light source.
Methods: The baseline radiation from UVA and UVB sources was measured at different distances from the photometers. Next, the radiation from the same sources was measured at the same distances, but transmitted by different types of glass. The baseline values were compared with the results after protection using glass.
Results: Laminated glass totally blocked UVA radiation, while smooth ordinary glass transmitted the highest dose (74.3%). Greater thicknesses of glass implied less radiation transmitted, but without a significant difference. Green glass totally blocked UVA radiation, while blue glass transmitted the highest dose of radiation (56.8%). The presence of a sunlight control film totally blocked UVA radiation. All glasses totally blocked UVB radiation.
Conclusion: The main characteristics of glass that make it a photoprotective agent are its type (especially laminated glass) and color (especially green), which give rise to good performance by this material as a barrier against the transmission of radiation.     

Protection of skin biological targets by different types of sunscreens

In vitro and in vivo studies provide a body of evidence that adequate protection of the skin against ultraviolet (UV)-induced damage requires photostable broad-spectrum sunscreens with a proper level of UVA protection. UVA alone and UV solar simulated radiation (SSR) induce DNA lesions in keratinocytes and melanocytes as reflected by the comet assay and p53 accumulation. UVA and SSR impair the immune system as shown by significant alteration of Langerhans cells and inhibition of contact hypersensitivity response to chemical allergens and delayed-type hypersensitivity response to recall antigens. Any of these detrimental effects is more efficiently prevented by sunscreens with a higher level of protection in the UVA range. The involvement of UVA (fibroblast alteration, increased metalloproteinase expression) and the pivotal need for well-balanced UVA/UVB sunscreens were further demonstrated using reconstructed three-dimensional skin models.     

The development of efficient sunscreens

Skin exposure to acute or repetitive ultraviolet light induces risks which are now well identified. An efficient photoprotection is thus required for both UVB and UVA radiation. In particular, increasing evidence of the detrimental effects of UVA on skin has led to the development of a new generation of sunscreens that provide effective protection throughout the whole UV radiation spectrum. Many new UV filters have been introduced in the last decade, particularly UVA filters, with improved efficacy and safety. Sunscreen filters must be carefully combined to achieve esthetically pleasing products offering photostable and well-balanced photoprotection.     

Electronic UV dosimeters

Background/aims: The pathogenic role of ultraviolet (UV) in the development of skin cancer, skin ageing and immunosuppression makes it important to monitor human exposure to UV radiation. In a previous study we constructed UVB and UVC dosimeters based on a thermoluminescent phenomenon induced by UV in CaF₂:Dy and CaF₂ crystals. However, these dosimeters were insensitive to UVA radiation and readout was time-consuming. In the present study we aimed to develop an electronic dosimeter suitable for UVA, UVB and UVC. The principle of this dosimeter is a measure of accumulated electric current induced by UV on a photodetector.
Methods: Electric current induced by UV on a photodetector was accumulated in a Plessey's E-cell coulometer. A special reading device was constructed to quantify total charge of the coulometer. Sensitivity for UVA, UVB and UVC was achieved by the use of appropriate filters in front of the photodetector.
Results: The sensitivity of the electronic dosimeter increased with increasing wavelength of UV radiation; therefore, in UVB and UVC dosimeters the use of amplifiers was necessary. A linear response to UVA, UVB and UVC was achieved.
Conclusion: Dosimeters with a linear response to increasing doses of UVA, UVB and UVC have been constructed for personal monitoring of UV exposure.     

In vitro assessment of the broad-spectrum ultraviolet protection of sunscreen products

BACKGROUND: There are considerable data to suggest that protection from solar ultraviolet (UV) radiation will reduce the risk of acute and chronic skin damage in humans. Whereas the sun protection factor (SPF) provides an index of protection against erythemally effective solar UV, largely confined to the UVB (290-320 nm) and short-wavelength UVA (320-340 nm) region, there is currently no agreed-upon method to measure broad-spectrum protection against long-wavelength UVA (340-400 nm). OBJECTIVE: The objective of these studies was to assess the potential of in vitro UV substrate spectrophotometry and subsequent calculation of the "critical wavelength" value as a measure of broad-spectrum UV protection and as a routine, practical procedure for classification of sunscreen products. METHODS: The spectral absorption of 59 commercially available sunscreen products and multiple experimental formulas with one or more UV filters was measured. Sunscreen product, 1 mg/cm(2), was applied to a hydrated synthetic collagen substrate, preirradiated with a solar simulator, and then subjected to UV substrate spectrophotometry. Multiple determinations from 5 independent samples per product were used to calculate the critical wavelength value, defined as the wavelength at which the integral of the spectral absorbance curve reached 90% of the integral from 290 to 400 nm. RESULTS: We found that a recognized long-wave UVA active ingredient such as titanium dioxide, zinc oxide, or avobenzone is a necessary but insufficient product requirement for achieving the highest proposed broad-spectrum classification, that is, critical wavelength of 370 nm or more. Although SPF and critical wavelength are largely independent of each other, UVA absorbance must increase commensurate with SPF to maintain the same critical wavelength value. Substrate spectrophotometry and the calculation of critical wavelength can readily account for sunscreen photostability by UV preirradiation. Finally, there is also a strong positive relationship between critical wavelength and a currently available in vivo measure of UVA protection. CONCLUSION: Determination of critical wavelength by means of UV substrate spectrophotometry provides a rapid, inexpensive, and reliable measure of broad-spectrum protection, which is largely independent of SPF, yet ensures long-wavelength UVA protection commensurate with SPF. The procedure provides a routine, sensitive means of differentiating and classifying sunscreen products and, importantly, obviates the need to subject volunteers to acute exposures of high-dose, nonterrestrial UV, the health risks of which are still poorly understood.     

Change in ultraviolet (UV) transmission following the application of vaseline to non-irradiated and UVB-exposed split skin

BACKGROUND: Topical preparations such as emollients used in combination with phototherapy can interfere with such treatment. OBJECTIVES: This study was performed to investigate the impact of vaseline on the ultraviolet (UV) transmission of non-irradiated split skin and on split skin previously exposed to UVB radiation. METHODS: Split-skin specimens were obtained from 20 patients. In each case, one sample was taken from an area of non-irradiated skin, while the second was taken from an area that had been previously exposed to UVB. The transmission was spectrophotometrically measured with split skin placed in specially designed quartz glass cuvettes before and after the application of two different amounts of vaseline (2.5 and 17.5 mg cm-2). RESULTS: Application of vaseline to skin previously exposed to UVB caused significant (P < 0.0001) changes in UV transmission in certain wavelength ranges. In the UVA range, a greater increase in transmission was achieved with 2.5 mg cm-2 vaseline, whereas in the UVB range, a greater increase was achieved with 17.5 mg cm-2 vaseline. The thicker the layer of vaseline applied, the lower was the difference in transmission between non-irradiated split skin and UVB-exposed split skin. CONCLUSIONS: Application of the correct amount of vaseline can enhance transmission in either the UVA or UVB range, and would enable dose reduction during a course of phototherapy.     

Solar ultraviolet radiation induces biological alterations in human skin in vitro: relevance of a well-balanced UVA/UVB protection

Cutaneous damages such as sunburn, pigmentation, and photoaging are known to be induced by acute as well as repetitive sun exposure. Not only for basic research, but also for the design of the most efficient photoprotection, it is crucial to understand and identify the early biological events occurring after ultraviolet (UV) exposure. Reconstructed human skin models provide excellent and reliable in vitro tools to study the UV-induced alterations of the different skin cell types, keratinocytes, fibroblasts, and melanocytes in a dose- and time-dependent manner. Using different in vitro human skin models, the effects of UV light (UVB and UVA) were investigated. UVB-induced damages are essentially epidermal, with the typical sunburn cells and DNA lesions, whereas UVA radiation-induced damages are mostly located within the dermal compartment. Pigmentation can also be obtained after solar simulated radiation exposure of pigmented reconstructed skin model. Those models are also highly adequate to assess the potential of sunscreens to protect the skin from UV-associated damage, sunburn reaction, photoaging, and pigmentation. The results showed that an effective photoprotection is provided by broad-spectrum sunscreens with a potent absorption in both UVB and UVA ranges.     

UV exposure in cars

BACKGROUND: There is increasing knowledge about the hazards of solar and ultraviolet (UV) radiation to humans. Although people spend a significant time in cars, data on UV exposure during traveling are lacking. The aim of this study was to obtain basic information on personal UV exposure in cars. METHODS: UV transmission of car glass samples, windscreen, side and back windows and sunroof, was determined. UV exposure of passengers was evaluated in seven German middle-class cars, fitted with three different types of car windows. UV doses were measured with open or closed windows/sunroof of Mercedes-Benz E 220 T, E 320, and S 500, and in an open convertible car (Mercedes-Benz CLK). Bacillus subtilis spore film dosimeters (Viospor) were attached to the front, vertex, cheeks, upper arms, forearms and thighs of 'adult' and 'child' dummies. RESULTS: UV wavelengths longer than >335 nm were transmitted through car windows, and UV irradiation >380 nm was transmitted through compound glass windscreens. There was some variation in the spectral transmission of side windows according to the type of glass. On the arms, UV exposure was 3-4% of ambient radiation when the car windows were shut, and 25-31% of ambient radiation when the windows were open. In the open convertible car, the relative personal doses reached 62% of ambient radiation. CONCLUSIONS: The car glass types examined offer substantial protection against short-wave UV radiation. Professional drivers should keep car windows closed on sunny days to reduce occupational UV exposure. In individuals with polymorphic light eruption, produced by long-wave UVA, additional protection by plastic films, clothes or sunscreens appears necessary.     

Evaluation of the capacity of sunscreens to photoprotect lupus erythematosus patients by employing the photoprovocation test

Although sunscreens are widely used to photoprotect patients with photosensitive lupus erythematosus (LE), standardized controlled studies that can prove their efficacy for this indication have been lacking. Therefore, in the present study, the capacity of three different, commercially available sunscreens to prevent the development of skin lesions that have been induced in LE patients under standardized, reproducible conditions by employing a provocative phototest was assessed. In a double blind, intraindividual comparative study, 11 patients with LE were photoprovoked according to a standard protocol. All patients developed LE-specific skin lesions upon photoprovocation with a combination of UVA plus UVB radiation. Each of the sunscreens tested prevented the development of skin lesions in this assay, but to various extents. Suncreen A (UVB: Octocrylene; UVA: Mexoryl SX, Mexoryl XL, Parsol 1789; TiO2) was by far the most effective by protecting in 11/11 patients. This protective capacity was corroborated by studies in which strong ICAM-1 mRNA expression was found in unprotected test areas, but not in sunscreen A pretreated sites. In contrast to sunscreen A, sunscreen B (UVB: Eusolex 6300, Parsol MCX, Uvinul T150, Neohelipan; UVA: Parsol 1789; TiO2) protected in 5 patients and sunscreen C (Eusolex 6300, Parsol MCX, Uvinul T150; UVA: Parsol 1789; TiO2) in 3 out of 11 patients. These studies indicate that the use of sunscreens is beneficial to LE patients because it can prevent the development of UV radiation-induced skin lesions. Effective protection, however, might vary considerably between different sunscreens.     

Do different ethnic groups need different sun protection?

Background: In the present study, the transmission of sunlight trough the human skin barrier into the living tissue was investigated in the spectral region between 280 and 700 nm.
Methods: The experiments were performed with a fiber-based spectrometer on sliced skin obtained from volunteers with different skin types. One fiber was positioned directly on the skin surface and the second one underneath the skin samples. The distribution of the sunlight under the epidermis was determined.
Results: Significant differences were found in the absorption properties of the different skin types, which were mainly determined by the variations in melanin concentration and distribution. It was found that sunscreens for specific ethnic groups need different combinations of UV filters, if a balanced relation between ultraviolet B (UVB) and ultraviolet A (UVA) protection is to be obtained. On the other hand, it could be demonstrated that the human skin is also well protected against visible and near-infrared light by melanin.
Conclusions: The higher the skin type category, the better the protection in the visible part of the spectrum of the sun. This stimulates the hot discussion at the present time, as to whether sunscreens should also contain protection compounds in the visible and near-infrared parts of the spectrum.