Physical sunscreens

Sunscreens absorb ultraviolet radiation before it can be absorbed in the skin. They are recommended to protect the skin from the major toxicities of sun exposure sunburn and skin cancer. Most available agents primarily absorb UVB, although newer preparations also provide protection against UVA. Physical sunscreens (which are generally opaque, hke titanium dioxide and zinc oxide) block all ultraviolet radiation. 

Various physical sunscreens such as heavy petroleum jelly, zinc oxide, titanium oxide, calamine are also used, which can stop and scatter ultraviolet rays... 

Fair-skiimed humans face a dilemma because ultraviolet light exposure carries the risks of carcinogenesis and skin aging, whereas insufficient ultraviolet light carries the risk of vitamin Ds (94, Fig. 11) insufficiency. The case is unique in so far as an endogenous biosynthetic pathway is subject to regulation by external lifestyle factors such as ultraviolet exposure and the use of chemical and physical sunscreens. Recent studies... 

Octyl methoxycinnamate Salicylates / Anthranilates Methyl salicylate Menthyl salicylate Menthyl anthranilate Octyl salicylate Physical Sunscreens... 

Anderson, M.W., Hewitt, J.P., and Spruce, S.R. (1997) Broad-spectrum physical sunscreens titanium dioxide and zinc oxide, in Lowe, N.J., Shaath, N.A., and Phatak, M.A. (Eds.) Sunscreens — Development, Evaluation and Regulatory Aspects, 2nd ed., New York Marcel Dekker, pp. 365-367. 

CAS 54392-26-6 EINECS/ELINCS 276-171-2 Uses W/o emulsifier for protective, baby care and general purpose emollient creams wetting agent and dispersant for physical sunscreens and decorative cosmetics... 

The main commercial apphcations for sahcylate esters are as uv sunscreen agents and as flavor and fragrance agents. Several have apphcation as topical analgesics. A number of sahcylate esters of commercial interest and their physical properties are hsted in Table 8. 

Physical agents include zinc oxide and titanium dioxide. These are the most effective sunscreens because they reflect UVA and UVB. When applied to the skin, they induce a white or ashen color, which many patients find cosmetically unacceptable. New micronized formulations of these agents are available which enhance cosmetic acceptability. Sunscreens... 

Sunblocks are opaque substances such as zinc oxide, titanium dioxide, and iron oxide that protect by forming a shield on the skin, which reflects and scatters incident radiation. In essence, sunblocks provide physical protection against sun exposure, including both visible and ultraviolet light. Sunscreens are substances that chemically absorb ultraviolet light in the top layer of the epidermis, protecting the underlying layers. 

A novel sunscreen system based on tocopherol acetate incorporated into solid lipid nanoparticles has been developed. In recent years, solid lipid nanoparticles (SLN) have been introduced as a novel carrier system for drugs and cosmetics. It has been found that SLN possess characteristics of physical UV-blockers on their own, thus offering the possibility of developing a more effective sunscreen system... 

The inactive ingredient is used at a level no higher than reasonably required to achieve its physical or technical function. For example, an antimicrobial excipient ingredient could only be used at a level consistent with preservation of the finished product (not at therapeutic levels), and a sunscreen ingredient could only be used at levels that protected the product from breaking down if the top of the jar was left open, not for protecting the user. 

Functional roles treated above are strictly organismal responses to biotic stresses. The use of chemical means to address physical stresses is largely nonexistent. A notable exception to this is the response many organisms make to harmful ultraviolet (UV) radiation. Sunscreens are small organic molecules which absorb UV radiation so that damage to DNA via cross-linking219 225 is prevented. Production of micosporin-like amino acids (MAA) appears to be widespread in shallow-water Antarctic marine invertebrates and macroalgae,223,224 which may be particularly adaptive at present because of the Antarctic ozone hole. 

Reflectant sunscreens. Inert minerals such as titanium dioxide, zinc oxide and calamine act as a physical barrier to UVB and UVA they are cosmetically unattractive but the newer micronised preparations are more acceptable. 

Protection against sunlight and prevention of skin infections are essential. Sunscreen ointments may occasionally provide some benefit, but physical avoidance of UVA radiation is usually necessary. Hypertransfusion and activated charcoal to decrease the enterohepatic circulation of porphyrin, hydroxyurea, intravenous heme, and antioxidant preparations have also been used to suppress erythropoiesis and porphyrin formation or to ameliorate the effects of porphyrin accumulation but none has been shown to have a reliable, long-term effect. Hemolytic anemia may require repeated transfusion and infusion of deferoxamine to prevent iron overload. 

Intermolecular hydrogen bonding resulting in a crystalline physical state crystalline sunscreens are difficult to incorporate in topical products and may result in an unacceptable product if the sunscreen agent is not solubilized properly... 

Protection from UVR is available through the use of sunsceens and clothing. Sunscreen lotions contain UVR absorbers and sun blockers contain pigment that physically blocks UVR. Hats, sunscreens, sunglasses and clothing can be used to decrease the exposure to ultraviolet radiation by a factor of 10 or more, as well as by people avoiding exposure to the sun at its maximum [74]. 

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