What makes a good sunscreen? – part 1


With summer here and holidays in the sun planned, we turn to buying sunscreens and the question arises:

What is a good sunscreen?

In my research into this question, I realise that this is not a simple question! My quest for an answer takes me through the following journey:

Why do we use sunscreen?

We tend to use a sunscreen to protect us from burning when out in the sun. But please remember that we do need some direct sunshine on our skin for our bodies to make Vitamin D (Read more about the benefits of Vitamin D here…)

How do they work?

Sunscreens are meant to protect us from the sun’s radiation & the possible damage it can cause.

The radiation from the sun has three different ultraviolet wavelengths – UVA, UVB & UVC.

Ultraviolet A and B enter the earth’s atmosphere but UVC doesn’t penetrate our atmosphere, so we don’t need to worry about that one.

UVA penetrates deeper int our skin and is associated with ageing of the skin as well as skin cancer. It can affect our skin all year and even through glass. Hence UVA is known as the ‘Aging Ray’.

UVB is more superficial on our skin and causes sunburn. It is the one we need to make Vitamin D. However, it is linked to particular types of skin cancer and is strongest spring to autumn between 10am to 4pm. UVB is known as the ‘Burning Ray’.

(Ref: The British Association of Dermatologists – sunscreen fact sheet-UVA-UVB)

For decades, both sunscreen manufacturers and users assumed that preventing or delaying sunburn would also avert other damage, such as skin cancer.

Sunscreens were invented to stop sunburn by reducing the absorption of UVB. They are commonly indexed by their SPF (sun protection factor) rating, which describes the product’s ability to prevent burning.

Today many experts realize that both UVA and UVB exposure may contribute to melanoma risk.

So many brands also show a five star rating which is the UVA protection factor. Another term you may see is ‘broad spectrum’ to cover both UVA & UVB protection.

(Ref: EWG – skin cancer on the rise)

What do these actually mean?

SPF tells you how much protection your sunscreen provides from UVB radiation while the star system tells you the percentage of UVA radiation that is absorbed by the sunscreen in comparison to how much UVB is absorbed.

So a high SPF sunscreen with no stars will offer protection from burning from UVB but no protection from UVA!

Also a low SPF with a high star rating provides low protection from UVB but still very little protection from UVA (since a high percentage of not much is very little!)

(ref: BBC: how does sunscreen work?)

Don’t be fooled by a high SPF!

We tend to assume we get twice as much protection from SPF 100 sunscreen as from SPF 50. But the extra protection is actually negligible. Properly applied SPF 50 sunscreen blocks 98 percent of UVB rays; SPF 100 blocks 99 percent.

When used correctly, sunscreen with SPF values between 30 and 50 offers adequate sunburn protection, even for people most sensitive to sunburn. Hence Australian authorities cap SPF values at 30 & European regulators at SPF 50.

(Ref: EWG – what’s wrong with high SPF?)

But SPF is just protection from UVB. UVA exposure suppresses the immune system, causing harmful free radicals to form in skin and is associated with higher risk of developing melanoma.

That’s why it’s important to choose a high SPF as well as a high UVA protection (ie. a high number of stars). Sunscreens that offer both UVA and UVB protection are sometimes called ‘broad spectrum’.

(Ref: The British Association of Dermatologists – sunscreen fact sheet-star system)

But it’s still prudent to remember that we usually don’t apply our sunscreen perfectly and it comes off with sweat or when rubbed with a towel. So be cautious with ‘extended wear’ or waterproof’ sunscreens, as we tend to just apply once and then think we don’t need to re-apply!

Remember – sunscreen is never as effective as it claims to be. So please reapply regularly to keep protected…

Other questions to research next include:

What are the safest sunscreens? Are there natural options? Are the environmental concerns of sunscreens?

Don’t get burnt…


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