SUNSCREEN & SUNSCREEN AGENTS : A REVIEW
*M.C.Sai HariKishan, C.P.Meher, S.M.Ahmed
Maheshwara Institute Of Pharmacy, Chitkul, Isnapur ,
Sunscreen agents are used to prevent sunburn. Limiting the exposure to the sun and using sunscreen agents when in the sun may help prevent early wrinkling of the skin and skin cancer. There are two kinds of sunscreen agents: chemical and physical. Chemical sunscreen agents protect from the sun by absorbing the ultraviolet (UV) and visible sun rays, while physical sunscreen agents reflect, scatter, absorb, or block these rays. Sunscreen agents often contain more than one ingredient. For example, products may contain one ingredient that provides protection against the ultraviolet A (UVA) sun rays and another ingredient that protects from the ultraviolet B (UVB) sun rays, which are more likely to cause sunburn than the UVA sun rays. Ideally, coverage should include protection against both UVA and UVB sun rays. The sun protection factor (SPF) that find on the label of these products tells the minimum amount of UVB sunlight that is needed with that product to produce redness on sunscreen-protected skin as compared with unprotected skin. Sunscreen products with high SPFs will provide more protection against the sun.The presented review article is concern with discussion on the sunscreen agents.
REFERENCE ID: PHARMATUTOR-ART-1664
Sunscreen(also commonly known as sunblock, sun tan lotion, sun screen, sunburn cream or block out) is a lotion, spray, gel or other topical product that absorbs or reflects some of the sun's ultraviolet (UV) radiation on the skin exposed to sunlight and thus helps protect against sunburn. Skin-lightening products have sunscreen to protect lightened skin because light skin is more susceptible to sun damage than darker skin. Depending on the mode of action sunscreens can be classified into physical sunscreens (i.e., those that reflect the sunlight) or chemical sunscreens (i.e., those that absorb the UV light). Sunscreens have traditionally been divided into chemical absorbers and physical blockers on the basis of their mechanism of action. Chemical sunscreens are generally aromatic compounds conjugated with a carbonyl group. These chemicals absorb high-intensity UV rays with excitation to a higher energy state. The energy lost results in conversion of the remaining energy into longer lower energy wavelengths with return to ground state. Physical blockers reflect or scatter UVR. Recent research indicates that the newer microsized forms of physical blockers may also function in part by absorption. Sometimes referred to as nonchemical sunscreens, they may be more appropriately designated as inorganic particulate sunscreen ingredients. Allowable ingredients and maximum allowable concentrations, as listed in the FDA monograph, are shown in the Table below. Sunscreen ingredients can also be classified by the portion of UVR that they effectively absorb. Encouraging photoprotection is the leading preventative health strategy used by physicians involved in skin care. Although sun avoidance is most desirable, outdoor occupations and lifestyles make total avoidance impossible for many individuals. The regular use of sunscreens represents a practical compromise in this regard. Sunscreens prevent the formation of squamous cell carcinomas in animals. In humans, the regular use of sunscreens has been shown to reduce actinic keratoses, solar elastosis, and squamous cell carcinoma.The routine use of sunscreens may also reduce melanoma risk.Drug photosensitization and photo-induced or photo-aggravated dermatoses may be prevented with sunscreen use, especially with products that offer better blockage in the UV-A range.
Sunscreen products are available with and without doctor's prescription. If we using this medicine without a prescription, carefully should read and follow any precautions on the label. If rash or irritation develops, stop using the sunscreen and check with your doctor. Sunscreen agents containing aminobenzoic acid, lisadimate, padimate O, or roxadimate may discolor and stain light-colored fabrics yellow. In addition to using sunscreen agents, it is advisable to minimize exposure to the sun from 10 a.m. to 2 p.m. (11 a.m. to 3 p.m. daylight savings time) when the sun is at its strongest. Take extra precautions also on cloudy or overcast days and around reflective surfaces such as concrete, sand, snow, or water, since these surfaces can reflect the sun's damaging rays. Wear protective clothing including a hat, long-sleeved shirt, and long pants. Sunglasses also should be worn to avoid sun damage to the eyes (cataract formation). Avoid sunlamps and tanning parlors because these can damage the skin and eyes as direct sunlight can. The following are skin types (complexions) and the appropriate sunscreen agent that should be used:
- Very fair; always burns easily; rarely tans—Use SPF 20 to 30.
- Fair; always burns easily; tans minimally—Use SPF 12 to 20.
- Light; burns moderately; tans gradually (light brown)—Use SPF 8 to 12.
- Medium; burns minimally; always tans well (moderate brown)—Use SPF 4 to 8.
- Dark; rarely burns; tans profusely (dark brown)—Use SPF 2 to 4.
Sunscreen agents are for external use only. These products usually come with patient directions. Carefull reading is needed before using any product. In choosing the sunscreen product, following point are considered for better effectiveness.
1.Type of Activity—Take precautions when you are in places of higher elevations (mountains) or on reflective surfaces (concrete, sand, snow, or water), as these may increase the likelihood of sun damage to the skin. Use a sunscreen with ultraviolet A/ultraviolet B (UVA/UVB) coverage and with a sun protection factor (SPF) of 15 or higher. Activities that make you sweat, such as outdoor jobs (gardeners, construction workers), outdoor sports (tennis) or exercise, prolonged sunbathing, or water sports such as swimming, water-skiing, or wind surfing, may result in the removal of the sunscreen agent from the skin. Use a water-resistant or waterproof sunscreen agent with SPF of 15 or more. When possible, also wear a hat, long-sleeved shirt, long pants, and UV-opaque sunglasses. Wearing UV-opaque sunglasses when you are in the sun is also necessary because the sun rays can cause cataracts.
2.Age—Do not use sunscreen agents on infants younger than 6 months of age. For children 6 months of age and older, use a lotion form of sunscreen with broad spectrum and SPF of 15 or higher. Avoid using alcohol-based sunscreen products for this age group.
3.Site of application—For the ear and nose, use a physical sunscreen agent. For the lips, use a gel-based lip sunscreen or lip balm.
4.Skin condition—If your skin is dry, use a cream or lotion form of sunscreen agent. If your skin is oily, use an alcohol or gel-based sunscreen. Avoid using alcohol-based sunscreens on eczematous or inflamed skin.
Various type of reagents are used in the preparation of the sunscreen products. some of the important reagents are briefly described below.
4-Aminobenzoic acid: It also known as para-aminobenzoic acid or PABA because the number 4 carbon in the benzene ring is also known as the para position.it is an organic compound with the formula H2NC6H4CO2H. PABA is a white grey crystalline substance that is only slightly soluble in water. It consists of a benzene ring substituted with an amino group and a carboxyl group.
The potassium salt is used as a drug against fibrotic skin disorders, such as Peyronie's disease1 PABA is also occasionally used in pill form by sufferers of irritable bowel syndrome to treat its associated gastrointestinal symptoms, and in nutritional epidemiological studies to assess the completeness of 24-hour urine collection for the determination of urinary sodium, potassium, or nitrogen levels.
Avobenzone : it is an oil soluble ingredient used in sunscreen products to absorb the full spectrum of UVA rays. It is a dibenzoylmethane derivative. Avobenzone exists in the ground state as a mixture of the enol and keto forms, favoring the chelated enol.2Its ability to absorb ultraviolet light over a wider range of wavelengths than many organic sunscreen agents has led to its use in many commercial preparations marketed as "broad spectrum" sunscreens. Avobenzone has an absorption maximum of 357 nm.3
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