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Most people apply sunscreen incorrectly

Written by Dr. Daliah Wachs
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A new study has found the majority of people miss the most vulnerable parts of their face when applying sunscreen.

Published in PLOS One, researchers from the University of Liverpool looked at the sunscreen application habits of 84 men and women with the majority avoiding areas of the face around the eyes.

However, study authors cite the skin around the eyes is the most vulnerable to sun damage and skin cancer.  SPF containing moisturizers were used even less around the eyes.

The Sun reports:

AUSTIN MCCORMICK, STUDY AUTHOR AND CONSULTANT OPHTHALMIC AND OCULOPLASTIC SURGEON, FROM AINTREE UNIVERSITY HOSPITAL TRUST, SAID: “THE EYELID SKIN IS VERY THIN AND THIS PUTS IT AT RISK OF UV DAMAGE.
“THE AREA AROUND THE EYELASHES AND BETWEEN THE EYELIDS AND THE NOSE IS LEAST LIKELY TO BE COVERED.”
MR MCCORMICK SAID THAT EYELID CANCERS ACCOUNTED FOR 10 PER CENT OF ALL BASAL CELL CARCINOMAS IN THE UK – THE MOST COMMON TYPE OF SKIN CANCER.
HE ADDED THAT MOISTURISER MAY BE USED MORE SPARINGLY BECAUSE IT IS OFTEN EXPENSIVE AND SOLD IN SMALLER AMOUNTS.

My theory:  We’ve been told since we were kids to keep things away from our eyes, especially lotions.

How do sunscreens work?

Sunscreens use chemicals to disperse or absorb UV rays.  Inorganic compounds in sunscreen such a titanium dioxide or zinc oxide attempt to scatter the UV rays.  Organic compounds such as PABA and oxybenzone attempt to absorb UV rays so they can’t damage the skin.

What’s the difference between UVA and UVB radiation?

UVA rays penetrate deeply into both the epidermis and dermis.  They can cause premature aging of the skin, wrinkles, and skin cancer.

UVB rays are shorter and primarily affect the epidermis. They are responsible for causing sunburns as well as skin cancer.

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What is SPF?

SPF stands for Sun Protection Factor.  The higher the SPF, the less sun photons enter the skin and cause damage.  SPF primarily measures the protection against UVB rays. We multiply the SPF factor by how long it takes one’s skin to burn by the SPF number to determine the protection factor.

In theory, an SPF of 30 suggests your skin, if it burns within 10 minutes without protection, will not burn until 300 minutes has lapsed (30 times 10).  However, we find this isn’t always the case.  People sweat or swim and the sunscreen dissipates.  Moreover many don’t put on the proper amounts (see below.)

So instead we use SPF as a grade to how much protection the product can offer.

An SPF of 15 blocks 93% of UVB rays

An SPF of 30 blocks 97% of UVB rays

An SPF of 50 blocks 98% of UVB rays

As we see, the relationship is not linear, however the higher the SPF, the more protection we have against UV rays..

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IMAGE FROM BADGERBALM

Although the SPF alludes to protection against burning, hence UVB rays, a sunscreen may still protect against both UVA rays and UVB rays if it’s a broad spectrum sunscreen.

 

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How to apply sunscreen

Most people apply sunscreen incorrectly or unevenly.   Lotion needs to be applied at an amount of 2mg/cm2 of skin or 1 teaspoon per body part (chest, arm, leg, face and neck).  It should be applied 15 minutes prior to going out into the sun and needs to be reapplied every 2 hours, or more often if swimming or sweating.

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Daliah Wachs is a guest contributor to GCN news, her views and opinions, medical or otherwise, if expressed, are her own. Doctor Wachs is an MD,  FAAFP and a Board Certified Family Physician.  The Dr. Daliah Show , is nationally syndicated M-F from 11:00 am - 2:00 pm and Saturday from Noon-1:00 pm (all central times) at GCN.