Sunscreens have been developed to prevent the short- and long-term damaging effects of UV irradiation. However, the sun protective factor (SPF), which is defined as the ratio of the minimal erythema dose (MED) of sun-protected skin divided by the MED erythema of non-sun-protected skin, gives only a quantitative level of protection against sunburn and edema. Therefore, there is an ongoing debate on the potency of sunscreens to protect against many other deleterious biological UV effects such as photoimmunosuppression, skin aging, or skin cancer. Recent efforts have been directed toward determining the end points of sunscreen efficacy, such as immune protection factor (IPF), mutation protection factor (MPF), and protection against photocarcinogenesis (Gil and Kim 2000). Although standardized phototest procedures are available and can be used as tools to evaluate the protective effects of sunscreens toward UV induction of LE lesions, studies addressing this important topic are lacking. Sunscreens may be subdivided into products using UV filters on a physical or a chemical base. Physical agents used in sunscreens are titanium dioxide, zinc oxide, talcum, kaolin, bentonide, silica, and mica, which protect against UVB and UVA irradiation. Physical sunscreens show, contrary to chemical filters, no potential for phototoxicity or allergenicity, and they are photostable, cost effective, and applicable to children as well as adults. Most physical sunscreens contain ZnO or TiO2 and are referred to as physical blockers because they provide at specified concentrations high SPF protection through absorption, scattering, and reflection of UV radiation in a wide spectral range. Especially since the development of micronized formulations of ZnO and TiO2, the cosmetic acceptability of physical sunscreens has increased, and physical sunscreens have gained growing interest. Chemical agents most often used include aminobenzoates (para-aminobenzoic acid), cinnamates (diethanolamine p-methoxycinnamate [Parsol]), salicylates (2-ethylhexyl salicylate), and benzophe-nones (dioxybenzone, sulisobenzone, and oxybenzone). Most chemical blockers contain a combination of different filters to block a higher percentage and a broader range of UV rays. Owing to different absorption peaks, chemical filters may protect against UVB alone, UVA alone, or combined UVB and UVA (Table 25.2). There are several hundred sunscreen formulations containing different UV-protective chemicals on the market. However, it is important to have the photoreactivity of a broadband absorbing sunscreen, which protects against UVB as well as UVA and exerts a high SPF (>15). This type of sunscreen has combinations of UVA and UVB filters and sometimes ZnO and TiO2.
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Rosacea and Eczema are two skin conditions that are fairly commonly found throughout the world. Each of them is characterized by different features, and can be both discomfiting as well as result in undesirable appearance features. In a nutshell, theyre problems that many would want to deal with.