Sunscreens can be classified into two major types: chemical and physical. Chemical sunscreens contain special ingredients that act as filters and reduce ultraviolet radiation penetration to the skin. These sunscreens often are colorless and maintain a thin visible film on the skin. Some sunscreens contain UVA and UVB absorbing chemicals.
Physical sunscreens are often referred to as sunblocks and contain ingredients such as titanium dioxide and zinc oxide which physically block ultraviolet radiation. Sunblocks provide broad protection against both UVA and UVB
Sunscreens are important skin-care products used to prevent photoaging and skin cancer. Until recently it was believed that blocking UVB radiation and sunburn were the only measures needed to prevent sun damage. The SPF rating was developed to measure the ability of a sunscreen to block UVB radiation. Now we know that UVA radiation also contributes significantly to damaging the skin. These chemicals are used in sunscreens to absorb UVB radiation only.
The PABA esters are padimate O, padimate A, and glyceryl aminobenzoate. These compounds are chemically similar to PABA. They provide effective protection in the range of 260 to 315 nm. The use of these formulations has declined with the popularity of the “PABA-free” claim. The PABA esters are fairly water resistant and do not stain clothing, but they can cause allergic reactions.
Octyl methoxycinnamate and cinoxate are cinnamates, derivatives of cinnamon. They are chemically related to balsam of Peru, tolu balsam, coca leaves, cinnamic aldehyde, and cinnamic oil. People with sensitivities to these chemicals may get an allergic reaction to sunscreen containing cinnamates. The cinnamates are much less potent than padimate O and require the addition of other UVB absorbers to achieve higher SPF’s. The cinnamates do not stain clothing. They are not water resistant and must be used in a thicker base or applied more frequently.
The salicylates are homomenthyl salicylate, and triethanolamine salicylate. Salicylates have been used for a long time, even before PABA. They are weaker UVB absorbers than PABA and are generally added to other formulations to boost the SPF. The salicylates are stable in the presence of sunlight and are water resistant however octyl and triethanolamine salicylate can cause skin irritation.
The benzophenones are oxybenzone and dioxybenzone. They are the second most commonly used components of sunscreens. They provide effective protection in the 320 to 340 nm portion of the UVA range but do not absorb the complete UVA spectrum. Oxybenzone is a more efficient UVB absorber and boosts the SPF when added to other UVB absorbers. The benzophenones do not stain clothing and do not cause skin irritation, however they are not water resistant.
Avobenzone is the only chemical that absorbs the whole UVA spectrum at 310 to 400 nm. It does not provide any UVB absorption. There has been controversy about whether avobenzone actually breaks down in the presence of sunlight, but it appears that these claims have not been backed up with further studies. It does not stain clothing and does not cause skin irritation
UVC – 100 to 290 nm
UVB – 290 to 320 nm
UVA – 320 to 400 nm
A nanometer is a distance of one billionth of a meter and is the unit used to describe wavelengths or electromagnetic radiation such as UV.
UVB affects the epidermis and is the primary agent responsible for sunburns. It is the most intense between the hours of 10:00 am and 2:00 pm when the sunlight is brightest. It is also more intense in the summer months accounting for 70% of a person’s yearly UVB dose. UVB does not penetrate glass.
UVA was once thought to have a minor effect on skin damage, but now studies are showing that UVA is a major contributor to skin damage. UVA penetrates deeper into the skin and works more efficiently. The intensity of UVA radiation is more constant than UVB without the variations during the day and throughout the year. UVA is also not filtered by glass.
Effects of UVA and UVB Radiation
Both UVA and UVB radiation can cause skin damage including wrinkles, lowered immunity against infection, aging skin disorders, and cancer. The process is still not fully understood. Some of the possible mechanisms for UV skin damage are collagen breakdown, the formation of free radicals, interfering with DNA repair, and inhibiting the immune system.
SPF stands for Sun Protection Factor. SPF 15 means your skin is protected from sunburn for up to 15 times longer than if you were not wearing sunscreen. No matter what your skin type, most dermatologists recommend an SPF of 15 or higher year-round. Higher SPF numbers protect your skin for longer times however no sunscreen gives total protection so you must be careful about how much time you spend in the sun. Regular use in the first 18 years of life could reduce the incidence of skin cancer.
When should sunscreen be used?
Sunscreen should be applied every daily to exposed skin, not just if you are going to be in the sun. While UVB rays cannot penetrate glass windows, UVA rays can, leaving you prone to these damaging effects if unprotected. For days when you are going to be indoors, apply sunscreen on the areas not covered by clothing, such as the face and hands. Sunscreens can be applied under makeup, or alternatively, there are many cosmetic products available that contain sunscreens for daily use because sun protection is the principal means of preventing premature aging and skin cancer. It's never too late to protect yourself from the sun and minimize your future risk of skin cancer.
Don't reserve the use of sunscreen only for sunny days. Even on a cloudy day, up to 80 percent of the sun's ultraviolet rays can pass through the clouds. In addition, sand reflects 25 percent of the sun's rays and snow reflects 80 percent of the sun's rays. (AmericanAcademy of Dermatology)
How much sunscreen should be used, and how often should it be applied?
Sunscreens should be applied to dry skin 15-30 minutes BEFORE going outdoors. When using sunscreen, be sure to apply it to all exposed areas and pay particular attention to the face, ears, hands and arms. Coat the skin liberally and rub it in thoroughly – most people apply only 25-50 percent of the recommended amount of sunscreen.7 One ounce, enough to fill a shot glass, is considered the amount needed to cover the exposed areas of the body properly. Don't forget that lips get sunburned too, so apply a lip balm that contains sunscreen with an SPF of 15 or higher.
Is sunscreen application all I need to do to protect myself from the sun?
No. Here is how to be Sun smart:
-Generously apply a broad-spectrum, water-resistant sunscreen with a Sun Protection Factor (SPF) of at least 15 to all exposed skin. "Broad-spectrum" provides protection from both ultraviolet A (UVA) and ultraviolet B (UVB) rays. Re-apply approximately every two hours, even on cloudy days, and after swimming or sweating
-Wear protective clothing, such as a long-sleeved shirt, pants, a wide-brimmed hat and sunglasses, where possible.
-Seek shade when appropriate, remembering that the sun's rays are strongest between 10 a.m. and 4 p.m. If your shadow is shorter than you are, seek shade. Protect children from sun exposure by playing in the shade, wearing protective clothing, and applying sunscreen.
-Use extra caution near water, snow and sand as they reflect the damaging rays of the sun, which can increase your chance of sunburn.
-Get vitamin D safely through a healthy diet that may include vitamin supplements. Don't seek the sun.8
-Avoid tanning beds. Ultraviolet light from the sun and tanning beds can cause skin cancer and wrinkling. If you want to look like you've been in the sun, consider using a sunless self-tanning product, but continue to use sunscreen with it.
-Check your birthday suit on your birthday. If you notice anything changing, growing, or bleeding on your skin, see a dermatologist. Skin cancer is very treatable when caught early. (AmericanAcademy of Dermatology)
How Do I Treat a Sunburn?
In case you forget to cover up and apply sunscreen, the resulting sunburn can be painful as well as dangerous. Remember that you may not immediately see the effects of overexposure to the sun. It may take up to 24 hours before the full damage is visible.
There are several types of burns and burn treatments. The two most common sunburns are first-degree burns and second-degree burns. First-degree sunburns cause redness and will heal, possibly with some peeling, within a few days. These can be painful and are best treated with cool baths and moisturizers or over-the-counter hydrocortisone creams. Avoid the use of "-caine" products (such as benzocaine), which may cause sensitivity to a broad range of important chemicals. Anti-inflammatory oral medications such as aspirin or ibuprofen may lessen the pain and discomfort associated with sunburn.
Second-degree sunburns blister and can be considered a medical emergency if a large area is affected. Do not break the blisters, as they are a natural protective mechanism to heal the affected area and rupturing them delays the healing process and invites potential infection. A layer of gauze may be used to cover the area until healed. When a burn is severe, accompanied by a headache, chills or a fever, seek medical help immediately. Be sure to protect your skin from the sun while it heals and thereafter.
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