The importance to use SPF daily

Our bodies were built to make good use of the sun. Sunlight helps keep our sleeping patterns on track so we can stay awake by day and sleep soundly at night. Getting too little sun, especially in winter months, can leave some people prone to a form of depression known as seasonal affective disorder. Sunlight also helps our skin make vitamin D, which is needed for normal bone function and health. Yet sunlight can also cause damage.
Sunlight travels to Earth as a mixture of both visible and invisible rays, or waves. Long waves, like radio waves, are harmless to people. But shorter waves, like ultraviolet (UV) light, can cause problems. There are three types or UV radiation: A, B and C.
Melanin in our skin protects it from the sun's ultraviolet rays, which can burn the skin, and over time, could reduce its elasticity and cause a person to age prematurely. Suntanning occurs because exposure to sunlight causes the skin to produce more melanin and to darken. The tan fades as these cells move toward the surface and are sloughed off.
Over time, exposure to these rays can make the skin less elastic. Skin may even become thickened and leathery, wrinkled, or thinned like tissue paper.
People who do not have much melanin and sun burn easily should protect themselves by covering up sensitive areas, wearing sun block, limiting their total exposure time, and limiting their sun exposure between peak hours. Clothing can also provide a great barrier against the sun’s UV rays.
How to choose the right sunscreen
There are two types of sunscreens: chemical sunscreens absorb ultraviolet radiation like a sponge, while mineral sunscreens containing titanium dioxide or zinc oxide reflect it back from the surface of the skin like a mirror.
According to skin cancer foundation, the SPF number tells you how long the sun’s UVB rays should take to redden your skin when using a particular sunscreen compared with the amount of time without sunscreen. So if you use an SPF15 product exactly as directed, it would take you 15 times longer to burn than if you weren’t wearing sunscreen.
Make sure you use broadspectrum sunscreen (protects against UVA and UVB) and be careful with water resistant ones as you can burn even when you are in water, so reapplying is key.
Avoid nanoparticles (particles smaller than 35 nanometres) as have been found potentially damaging to humans as they may enter the bloodstream and cause allergic reactions. However, sunscreen manufacturers are not legally obliged to reveal the size of the nanoparticles they use, making extra-conscious shopping tricky.
My personal choice is zinc oxide and titanium dioxide as it might be less likely to cause skin irritation in people to have sensitive skin and have also been proposed for the FDA as “generally recognized as safe and effective” (GRASE).
National Institutes of Health magazine July 2014 edition
Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.