THE SCI­ENCE OF SUN­SCREEN

Your Family - - Health Now - Source: Lives­cience.com

The sun’s out, and in true South African style we’ll be beach­ing and braaing our way through the hol­i­days. By now ev­ery­one knows the dan­gers of sun dam­age to your skin and that you should be wear­ing sun­screen at all times, but are you us­ing it cor­rectly? How does sun­screen ac­tu­ally work?

WHAT’S IN THEM?

Sun­screens work in a few dif­fer­ent ways. They usu­ally con­tain in­or­ganic chem­i­cals like zinc ox­ide or ti­ta­nium diox­ide, which ac­tu­ally re­flect UV rays away from your skin. Re­mem­ber the thick, white, paint-like sun­screen noses peo­ple sported in the 80s and early 90s? They were slathered in those in­or­ganic com­pounds. Nowa­days, the par­ti­cles of these com­pounds are much smaller and prac­ti­cally in­vis­i­ble. Sun­screens also of­ten con­tain or­ganic chem­i­cals, like avoben­zone or oxy­ben­zone. Rather than de­flect­ing the UV light, the mol­e­cules ab­sorb the UV ra­di­a­tion through their chem­i­cal bonds. As the bonds ab­sorb the ra­di­a­tion, the com­po­nents of the sun­screen break down and re­lease heat.

WHAT IS SPF, RE­ALLY?

SPF stands for sun pro­tec­tion fac­tor, and refers to how well the sun­screen pro­tects against one type of UV ra­di­a­tion, called UVB. These are the rays most re­spon­si­ble for sun­burn and skin can­cer.

UVA ra­di­a­tion is dif­fer­ent. It pen­e­trates deep into the skin and causes pre­ma­ture age­ing, wrin­kling and age spots, as well as in­creas­ing the risk of cer­tain skin can­cers. Look for sun­screens la­belled ‘broad spec­trum’ that block against UVB and UVA.

It’s gen­er­ally rec­om­mended you use sun­screen with an SPF be­tween 15 and 50 (SPF rat­ings higher than 50 have not been proven to be more ef­fec­tive than SPF50). An SPF of 15 pro­tects against about 93% of UVB rays, and an SPF of 30 pro­tects against 97% of rays, ac­cord­ing to the Mayo Clinic. No SPF can block 100% of UV rays.

Be­cause some UV ra­di­a­tion is bound to make it through the sun­screen to your skin, the SPF num­ber refers to about how long it would take for your skin to red­den while you’re wear­ing the sun­screen. This means an SPF of 15 should pre­vent your skin from red­den­ing for ap­prox­i­mately 15 times longer than without the sun­screen.

Use roughly a shot-glass worth of sun­screen for each ap­pli­ca­tion and reap­ply ev­ery two hours, to en­sure it ac­tu­ally pro­tects your skin.

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