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All About Sunscreen

spf sunscreen

Sunscreens are topical products that absorb or reflect some of the sun’s ultraviolet (UV) radiation and thus helps protect against sunburn. They act as a shield against the UV rays and should be used whenever your skin is exposed to the sun, no matter the season.

Here’s everything you need to know about the types of sunscreens and what might work best for you.

Why Do I Need Sunscreen?

Sunscreen plays a key role in protecting your skin from the sun. When you use a broad-spectrum sunscreen with SPF 30 or higher, it can:

  • Prevent sunburn.
  • Prevent pigmentation or darkening of the skin.
  • Decrease signs of aging.
  • Reduce your risk of developing skin cancer.
  • We should enjoy the outdoors, and by applying a good sunscreen, we can have fun in the sun.

Which Sunscreen Should I Use?

There are several types of sunscreens available:

  • Chemical sunscreens work like a sponge, absorbing the sun’s rays. They are easier to rub into the skin without leaving a white residue.
  • Physical sunscreens (also known as sunblock) act like a shield. They reflect the sun’s rays and they are better for sensitive skin.
  • Broad Spectrum: The words “broad spectrum” means that the sunscreen can protect your skin from both types of harmful UV rays — UVA rays and the UVB rays.
  • SPF 30 or higher: The American Academy of Dermatology recommends an SPF of 30 or higher, which blocks 97 percent of the sun’s rays. Higher-number SPFs block slightly more of the sun’s rays, but there is no sunscreen that will block 100 percent of the sun’s rays.
  • Water Resistant: Look for the words “water resistant.” This tells you that the sunscreen will stay on wet or sweaty skin for a while before you need to reapply. Water resistance lasts either 40 or 80 minutes. Not all sunscreens offer water resistance.

Which Formulation Should I Use?

There are many different formulations of sunscreens. Gels are great for hair areas and for people who want a quick-drying sunscreen. Titanium dioxide or zinc oxide sunscreens are better for sensitive skin. Creams are best for dry skin and the face. It is always better to consult a certified dermatologist to know which sunscreen would be best for your skin.

What is SPF?

SPF means Sun Protection Factor. It is commonly interpreted as how much longer the skin covered with sunscreen takes to burn compared with unprotected skin. So, for example, if you burn after 10 minutes in the sun, then using a sunscreen labelled with SPF 15, is taken to mean that you can safely remain in the sun for 10 × 15 = 150 minutes, before burning.

  • SPF 15: Blocks 93 percent of the sun’s UVB rays
  • SPF 30: Blocks 97 percent of the sun’s UVB rays
  • SPF 50: Blocks 98 percentof the sun’s UVB rays

There is commonly held, but false, belief that applying an SPF 30 sunscreen gives very little additional benefit to using an SFP 15 sunscreen. The basis of the argument is that SPF 15 absorbs 93 percent and SPF 30 absorbs 97 percent of solar UV — a difference so small that it is of little benefit (see above).

What is important to skin health is not what is absorbed by the sunscreen but how much UV reaches the skin. So, in the case of an SPF 15 product, the skin exposure relative to unprotected skin for a given time in the sun is 1/15 = 7 percent, while for an SPF 30 product, the relative exposure is 1/30 = 3 percent. In other words, twice as much UV reaches the skin when an SPF 15 product is applied than when the same quantity of SPF 30 is applied.

How Should I Apply Sunscreen?

  • Apply sunscreen generously before going outdoors. It takes approximately 15 minutes for your skin to absorb the sunscreen and protect you. If you wait until you are in the sun to apply sunscreen, your skin is unprotected and can burn.
  • Apply enough sunscreen to cover all exposed skin. About a teaspoon is needed to cover the head and neck.
  • Do not rub the sunscreen into your skin, but spread the sunscreen uniformly over the surface of the skin and allow to dry.
  • To remain protected when outdoors, reapply sunscreen every three hours, or immediately after swimming or sweating.
  • Apply even on cloudy days and in winter: Your skin is exposed to the sun’s harmful UV rays every time you go outside, even on cloudy days and in the winter. So, whether you are on vacation or taking a brisk fall walk in your neighborhood, remember to use sunscreen.
  • Reapply as directed: Sunscreen needs to be reapplied after swimming, excessive sweating, rubbing or towel drying.

What Other Precautions Should I Take?

  • Clothing: Wear a wide-brimmed hat which will cover your ears and face. Choose lightweight, dark-colored, tightly woven, long-sleeved cotton clothes. Wear sunglasses with UV protection.
  • Shade: Seek shade or try to remain indoors, especially from 10:00 a.m. to 2:00 p.m. when the sun’s rays are the strongest.
  • Reflection: Be careful around water, sand and concrete (and snow in the winter). These surfaces reflect the sun’s rays, increasing your chance of sunburn.
  • Expiration dates: Sunscreens do expire, so discard any with expired dates. If there is no expiration date on the bottle, there are some signs that the sunscreen may no longer be good. Changes in the color or texture of the sunscreen means the sunscreen is no longer protective.

Is Sunscreen Safe?

Some of the older sunscreens were known to cause allergic reactions. However, most of the newer formulations are hypoallergenic, which means that they are unlikely to cause an allergic reaction. A certified dermatologist can help you find out which sunscreen is best for your skin.

The Environmental Working Group rates the best sunscreens every year. Here is the 2019 guide to sunscreen safety ratings.

About the author

Dr. Siddhartha Saikia

Dr. Siddhartha Saikia is a consultant dermatologist in Gandhinagar, India, and is interested in the latest information on health, fitness and skin care. Visit his website https://saikiaskin.care

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