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Sunscreen - not just for the summer

Updated: Feb 6, 2023

Everyone knows the importance of wearing sunscreens to prevent skin cancer. Despite advice to use skin protection, skin cancer is rising at an alarming rate.

Read on if you want to learn the facts from the fiction.


What does Sunlight contain?

Sunlight is made up of several rays called radiation. Radiation is placed into categories depending on the ray’s wavelength (or how “big or long” the rays are).

As you can see from the diagram below, 40% of light is made up of visible light (what you see) and infrared light (what you can’t see).

Image 1

The 10% left is UVB and UVA. Added together, UVA and UVB comprise UltraViolet Radiation or UVR.

UVA is further divided into UVA1 (aka short UVA) and UVA2 (aka long UVA).

UVB is not only for (Holiday) Burning

Although UVB only makes up 0.5% of the light reaching the earth (20 x less than UVA), it is enough to cause Burning when you are exposed to the sun (B = Burning).

UVB facts

  • UVB damages the outermost layers of your skin.

  • UVB is the cause of suntan, sunburn and blistering.

  • Sun Protection Factor (SPF) on labels of sunscreen products is only a measure of UVB protection.

  • The amount of UVB changes during the day, peaking between 10 am and 4 pm.

  • UVB rays do not penetrate glass.

UVA - ageing all-day

UVA hits the earth “all day long”. UVA is responsible for Ageing, such as thickened skin and wrinkles. This is easy to remember as A = Ageing.

As UVA has a longer wavelength, it penetrates deeper into the skin, where most skin cancers occur.

Unlike UVB, UVA can pass through clouds, windows and car windscreens.

Image 2

UVA facts

  • UVA forms 95 per cent of the UV radiation reaching the earth throughout the year.

  • UVA rays also cause tanning and sunburn.

  • A broad-spectrum sunscreen protects you from both UVA and UVB

What skin changes are caused by sunlight?

Sun is thought to be the leading cause of premature ageing of the skin. This is also called photo-ageing.

Signs of Sun Damage

Signs of sun damage, with the main perpetrator highlighted in (brackets), include:

  • Reduced collagen levels (UVB)

  • Areas of thick skin (UVB)

  • Areas of thin skin (UVA)

  • Wrinkles (UVA)

  • Dark pigment spots on the skin (called liver or sun spots - UVA)

  • Solar elastosis (yellow, thickened skin - UVB)

Solar Elastosis

Solar elastosis describes skin that appears yellow and thickened due to sun damage.

Actinic Keratosis

Actinic Keratoses are areas of rough, dry patches of skin due to sun damage.

What skin cancers are caused by UVR

There are three primary skin cancers thought to be linked to sun exposure:

  1. Basal cell carcinoma (BCC)

  2. Squamous cell carcinoma (SCC)

  3. Melanoma

You are more likely to develop BCC and SCC if you:

  • Live in a sunny area.

  • Spend a lot of time in the sun.

  • Have signs of photo-ageing.

Melanoma is linked to intermittent rather than constant sun exposure (like taking vacation holidays).

A history of previous sunburn puts you at risk of all three.

Sunscreens and preventing skin cancer

The first sunscreens used to only block UVB. However, UVA is one of the main risk factors for the development of melanoma,

Sunscreens should therefore block both UVA and UVB.

Tanning beds and the risk of skin cancer

Sun beds and lamps produce an artificial form of ultraviolet light (mainly UVA) and are linked to all three types of skin cancer mentioned above.

As they are a cause of cancer, sunbeds are regarded as carcinogenic.

The risk of BCC and SCC is higher if indoor tanning is started before the age of 25.

The risk of melanoma is higher if indoor tanning is started before the age of 30.

What should you do in addition to applying SPF?

Even though wearing a daily broad-spectrum sunscreen is essential, we know this is not enough.

Other “skin-protecting behaviours” should include:

  • Staying in the shade.

  • Wearing SPF-rated clothing.

  • Wearing hats (provides an SPF of 5).

  • Wearing UV-blocking sunglasses.

  • Sun avoidance - not going in the sun between 10 am and 4 pm.

Sun protection with clothing

The ability of clothes to block the sun is graded using an Ultraviolet Protection Factor (UPF).

The UPF is improved by washing your clothes and using detergents containing UV-absorbing agents.

Do you need to wear Sunscreen if your foundation or makeup contains SPF?

In a word, yes.

Foundation is used in insufficient amounts to deliver the SPF on the label. To be effective, you need a lot!

I use a high-SPF sunscreen; surely that is ok?

SPF applies to UVB protection only. It provides no information about protection against UVA.

An SPF of 10 means you can stay in the sun 10 times longer before you become red.

Sunscreen versus Sunblock

No sunscreen completely blocks the sun, and “sunblock” is considered misleading.

In the USA, sunblock has been “banned” on Sunscreen bottle labels.

Applying sunscreen - enough is not enough!

It is well known that we don’t apply enough sunscreen.

“Enough” means applying sunscreen to a proper thickness and spreading it evenly.

35ml is the minimum amount of sunscreen to cover the whole body.

The reality is that most users only give themselves 20-50% protection. That is, we only apply 7ml to 17.5ml. This means an SPF of 15 is only 5!

All sunscreens lose their effectiveness with time when exposed to the sun's rays. This is why we must keep applying every 2-3 hours throughout the day.

Jumping in the Sea? Are sunscreens really waterproof?

Waterproof is no longer allowed in sunscreen labelling as no sunscreen is completely waterproof. The correct terminology is “water-resistant”.

Can you measure the amount of UVA protection?

“Yes and No” as the best test has yet to be universally agreed upon. Until then, in Europe, we use the “PFA method” developed by Johnson & Johnson, which measures tanning - confusingly a UVB phenomenon.

Chemical versus the Physical

There are two types of sunscreen - physical and chemical.

Chemical sunscreens absorb UV radiation but release free radicals and may cause allergies.

Physical sunscreens reflect UV rays, but not all of them.

Chemical sunscreens - The race to work

Chemical sunscreens take up to 20 minutes to provide complete protection. They also heat up when in the sun due to a chemical reaction.

Chemical sunscreens are easier to apply, colourless and more user-friendly. They are commonly combined with a physical sunscreen.

Sensitive skins may react to some of the chemicals used - most people wrongly think this is an allergy which, fortunately, is very rare.

Physical Sunscreen - Effective but Cloggy

Physical sunscreens block the broadest range of light, are not absorbed and rarely cause allergic reactions, so they are better tolerated by most skin types. They also work straight away.

Unfortunately, physical sunscreens have a white appearance on the skin, are thicker and more challenging to apply.

Physical sunscreens reflect rather than absorb UV radiation.

The best-known physical sunscreens contain Zinc or Titanium oxide.

The Zinc Sunscreen Wonder

Aside from being a physical sunblock, Zinc has many beneficial properties useful in skincare:


  • It is anti-itching

  • It is antibacterial

  • Helps with hair regrowth

When should you apply sunscreen?

Sunscreen should always be applied 30 minutes before sun exposure, especially on the beach.

Sunscreen should also be applied directly onto the skin before any makeup.

Sunscreen and Sun Protection Videos | FDA

Sunscreen and vitamin D

Your skin makes vitamin D naturally when exposed to the sun's rays. Much of the controversy surrounding regular sunscreen use is about whether they reduce vitamin D levels.

Vitamin D has many functions, including reducing the risk of melanoma.

Do sunscreens reduce vitamin D levels?

Most likely not. But regardless, the risks of sun exposure without sunscreen outweigh the effects of sunscreens on vitamin D.


Effectiveness, compliance and application of sunscreen for solar ultraviolet radiation protection in Australia, Stuart I Henderson, Kerryn L King, Ken K Karipidis, Rick A Tinker, Adele C Green

The effect of sunscreen on vitamin D: a review. R.E. Neale, S.R. Khan, R.M. Lucas, M. Waterhouse, D.C. Whiteman, C.M. Olsen.

How many melanomas might be prevented if more people applied sunscreen regularly? C.M. Olsen, L.F. Wilson, A.C. Green, N. Biswas, J. Loyalka,D.C. Whiteman.


Images 1 and 2 screenshot - from Baumann's Cosmetic Dermatology, 3rd Edition. By Leslie S. Baumann, Evan A. Rieder, Mary D. Sun © 2022 | Published: May 31, 2022

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