What are sunscreens?
June 30, 2016 • the kimmel institute • Vein Clinic
From the desk of Alice Rodriguez Brockwell, ARNP
Board Certified Nurse Practitioner
What are sunscreens?
Sunscreens are chemical agents that help prevent the sun’s ultraviolet (UV) radiation from reaching the skin. Two types of ultraviolet radiation, UVA and UVB, damage the skin and increase your risk of skin cancer. The ingredients in sunscreen protect the skin by absorbing, blocking or scattering UVA radiation. UVB is the chief culprit behind sunburn, while UVA rays, which penetrate the skin more deeply, are associated with wrinkling, leathering, sagging and other effects of photo aging. They also exacerbate the carcinogenic effects of UVB rays, and increasingly are being seen as a cause of skin cancer on their own. Sunscreens vary in their ability to protect against UVA and UVB.
Who should use sunscreen?
Anyone over the age of six months should use a sunscreen daily. Even those who work inside are exposed to ultraviolet radiation for brief periods throughout the day. Also, UVA is NOT blocked by most windows.
What is SPF?
SPF- or Sun Protection Factor- is a measure of a sunscreen’s ability to prevent UVB from damaging the skin.
SPF 15 blocks approximately 93 percent of all incoming UVB rays. SPF 30 blocks 97 percent; and SPF 50 blocks 98 percent. They may seem like negligence differences, but if you are light-sensitive, of have a history of skin cancer, those extra percentages will make a difference.
But there are problems with SPF model: First, no sunscreen, regardless of strength, should be expected to stay effective longer than two hours without application. Second, “reddening” of the skin is a reaction to UVB rays alone and tells you little about what UVA damage may be getting. Plenty of damage can be done without the red flag of sunburn being raised.
What is PA?
Newer sunscreens in the market also contain UVA- filters and their protective effect against UVA is measured with PA. PA stands for Protection Grade of UVA. The FDA currently does not offer a rating system for UVA. PA is a designation that originated is Asia and is used globally.
UVA is long wavelength (320-400 mm) UV. UVA radiation can penetrate glass and clouds and can be 30to 50 times more prevalent than UVB rays. UVA rays can penetrate into the deep layers of the skin and cause skin aging, wrinkles and skin cancers.
How to choose Sunscreen?
Select a sunscreen that provides broad-spectrum protection, UVA / UVB protection. Look for sunscreen with zinc oxide and/ or titanium dioxide. These ingredients are insoluble particles which absorb and reflect UV away from the skin.
How to apply Sunscreen?
Sunscreen should be the last step of skin care regimen so that it can shield your skin and block UV rays. Apply sunscreen after applying moisturizer.