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Sunscreen: How to Use Correctly

Medically Reviewed
Key Takeaways

1. Sunscreen should be used daily, applied at least 15 minutes before you leave the house. Remember to reapply every two hours, or earlier if you are sweating profusely or swimming.

2. Ensure a sufficient amount of sunscreen is applied on all exposed skin. Most adults need about 1 ounce (or 30g) to fully cover their body.

Sunscreen: Why Do We Need It?

SPF only represents protection against UVB rays and the numerical value simply indicates how long one can stay out in the sun without burning​.

Prevent sun damage, premature ageing and skin cancer with good sunscreen.

Most people would agree that sunscreen is an essential part of skincare routine.

However, not everyone practises what they preach while others may be overwhelmed by the wide range of sunscreens and the many different labels, textures, ingredients and SPF values available.

Indeed, in all its varied forms, sunscreen has become a skincare staple, for good reason. Studies have shown that basking in the sun can lead to premature ageing and can even have life-threatening consequences.

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The culprits are the sun’s ultraviolet A (UVA) and ultraviolet B (UVB) rays. The former are long rays that penetrate the skin deeply and contribute to ageing, while the latter are short rays that cause skin reddening and sunburn. Both can increase the risk of skin cancer.

In a recent report by the Singapore Cancer Registry tracking cancer trends from 2017-2021, skin cancer was the sixth most frequently occurring cancer in Singaporean men and the seventh for Singaporean women.

Sun worshippers should note that there’s no benefit to spending long periods unprotected in the sun. 

“Prolonged sun exposure causes photo-ageing, which is the main cause of skin reactions such as DNA mutation. Photo-ageing can result in changes in skin texture and blood vessels, and cause pigmentation and abnormal growths,” advised Clinical Associate Professor Pang Shiu Ming, Senior Consultant from the Department of Dermatology at Singapore General Hospital (SGH), a member of the SingHealth​ group.

What does SPF stand for?

SPF stands for Sun Protection Factor. It measures how well a sunscreen protects the skin from UVB rays.

For example, if your skin would normally burn after 10 minutes in the sun, applying an SPF 15 sunscreen allows you to stay in the sun without burning for approximately 150 minutes (a factor of 15x longer).

Does higher SPF offer higher protection?

A sunscreen with a higher SPF value does not necessarily translate to better sun protection. 

SPF only represents protection against UVB rays and the numerical value simply indicates how long one can stay out in the sun without burning.

So if it takes 15 minutes for the skin to start burning, SPF 15 sunscreen will allow one to bask in the sun for 15 times longer without burning. 

Also, sun protection does not increase proportionally with SPF. ​“An SPF of 15 indicates 93 per cent protection whereas an SPF of 34 indicates 97 per cent.

In the higher ranges of SPFs, the difference is less meaningful. A sunscreen with SPF 60 only provides about 2 per cent more protection than one with SPF 30,” said Dr Pang, adding that sunscreens with SPF 15 will suffice for people working indoors.

When to use sunscreen and how to apply properly?

Sunscreen should be used every day. One should apply a sunscreen at least 15 minutes before leaving the house. Reapply sunscreen every two hours or earlier, especially while swimming or if there is profuse sweating.

Consider using a sunscreen indoors, as typical home and office windows block most UVB rays but only a smaller portion of UVA rays. Installation of solar window films can block out the UVA rays.

Sufficient sunscreen should be applied to cover all exposed skin. Most adults need about 1 ounce (or 30g) to fully cover their body. Do not forget the neck, ears and top of the head (for individuals with sparse hair).

More tips to stay protected from the sun

  1. Avoid going out in the sun from 9.00am to 5.00pm. As a rule of thumb, if your shadow is shorter than you, you should be seeking shade.
  2. Avoid tanning beds and salons.
  3. Wear a wide-brimmed hat, use an opaque umbrella, sun-safe clothing and wear sunglasses when possible.
  4. Extra caution is needed near water, snow and sand, as the sun’s rays may be reflected and can increase the risks of sunburn.
  5. Do not omit sunscreen on a cloudy day as majority of the sun’s UV rays can hit your skin.

How to balance having sufficient vitamin D and be safe from the sun?

Optimal sunscreen use for daily protection does not compromise vitamin D synthesis in healthy people.

Sensible sun exposure before 9.00am and after 5.00pm, intake of foods rich in vitamin D and/or vitamin supplements help to ensure adequate vitamin D levels.

Screening for vitamin D status and supplementation are recommended in patients with photosensitivity disorders

Ref: H24 (ed)

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Skin Cancer: Symptoms, Treatment and Prevention Tips

The 3 Essentials for Beautiful Skin

5 Top Foods for Great Skin

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