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Sunscreen: A Deep Dive

Updated: Nov 24, 2020

I've been meaning to write this post for a long time, but this is a HUGE topic and I wanted to be exhaustive. So buckle up, because it's going to be a long one!

Let's start with WHY we need to protect our skin from UV.

UV radiation from the sun, damages our skin cells. More specifically, it damages the DNA within our cells, causing mutations in the genetic code. These mutations create gaps in the genetic information required for our cells to divide into new healthy cells.

Over a lifetime of exposure, that damage is cumulative. It can (and will) have significant consequences for our health - and I'm not just talking aesthetics here, I'm talking about the health and function of your body's largest organ (making up around 16% of your total body mass).

Some possible consequences of a lifetime of unprotected UV exposure include: skin cancers such as basal cell carcinomas, squamous cell carcinomas, and malignant melanomas (which, let's not forget, can metastasise and develop into other cancers), skin atrophy or hypertrophy (excessive thinning or overgrowth), reduced ability for cellular repair resulting in slower wound healing, and reduced immune function leading to an increased likelihood of skin infections.

In terms of what you'll see in the mirror: telangiectasia formation (visible red blood vessels), thinning of the dermis (deeper layer of the skin) and/or excessive thickening of the outer layer of the skin, pigmentation ("age spots", freckles), formation of wrinkles and lines, overall dull or sallow complexion, enlarged pore size, and "sagging" or skin laxity. Your skin will look worse on the outside, because it is no longer functioning properly on in the inside.

The good news is, much of this damage is PREVENTABLE - if we only take the time to protect our skin properly.

Now let's talk about UV itself.

UV radiation is classified as a "complete carcinogen", because it is both a mutagen (able to alter your DNA and increase the likelihood of genetic mutations), a damaging agent, and it has the properties of both a tumor initiator, AND a tumor promoter. UV exposure is THE most important controllable risk factor for skin cancer.

There are three types of UV: UVA, UVB, and UVC. The types most relevant to us are UVA and UVB.

UVC is completely absorbed by the earths ozone layer, so our exposure to it on earth is limited - we can only really be exposed with the use of mercury lamps, welding torches and old school tanning beds.

UVB is only partially absorbed by the ozone layer, so we DO get exposure to it on earth. UVB (or "UVBurn" as I like to call it) is responsible for most sunburns, and is strongly linked to skin cancer development. Intensity of our exposure to UVB varies depending on time of day, season, and location in the world. Interestingly, damage from UVB actually takes time to become apparent. You might have noticed sunburns can take hours to fully develop - you can leave the beach looking fine, and only have your sunburn become visible a few hours later .

UVA accounts for around 90% of all of our UV exposure. It penetrates deeper than UVB, causing damage to the deeper layers of the skin. UVA is present to the same degree regardless of cloud cover, season, location, time of day (as long as the sun is still up), and is still causing DNA damage in your skin. This is the reason you still need to wear sunscreen on a cloudy day - as long as there's daylight, there's damage being done.

Now for the age old question: If I have darker skin, do I need to wear sunscreen?

The answer: darker skin IS at a much lower risk of developing skin cancer due to the UV protective qualities of the skin's higher melanin content. But that doesn't mean the skin cannot be damaged, particularly by UVA which penetrates into the deeper layers of the skin. Melanin provides some protection, but not complete protection.

Not only that, but darker skin is more prone to developing PIH (post-inflammatory hyperpigmentation), AKA the dark marks that are left behind after trauma to the skin, usually acne/breakouts. UV exposure increases the risk of developing PIH and can darken existing PIH.

The darkest human skin tones have a natural protection of around SPF13 - we recommend everybody wear sunscreen SPF30+, regardless of skin colour/tone.

CHEMICAL vs PHYSICAL - What does it mean?

Chemical sunscreens once applied, sit within the upper layer of the skin and absorb UV rays. There are a multitude of active ingredients that can make up a chemical sunscreen, including: oxybenzone, homosalate, octocrylene, avobenzone, and more. Chemical sunscreens do have a higher chance of causing irritation to the skin, some active ingredients more than others - but they also tend to have a lighter consistency than physical sunscreen, so can be better for oily/congested skins.

Physical sunscreens once applied, sit on top of the skin and reflect UV rays. There are only two active ingredients for use in physical sunscreens: Zinc Oxide and Titanium Dioxide. Physical sunscreens tend to be less likely to irritate - but can be a little heavier in consistency than their chemical counterparts.

Is SPF15 enough?

Not really. SPF30 or 50 is ideal. There's actually not a huge difference between SPF30 and SPF50 - read the guide below:

SPF15 - blocks around 93% of UVB rays

SPF30 - blocks around 97% of UVB rays

SPF50 - blocks around 98% of UBV rays

What does SPF actually mean?

SPF only indicates UVB protection. So how do we measure UVA protection?

First off, if a sunscreen protects against both UVA and UVB, it will have the label "broad spectrum". If it doesn't, it only protects against UVB.

Physical sunscreens are ALL broad spectrum, as their active ingredients both protect against UVA and UVB. However not all chemical sunscreens are broad spectrum, because most chemical sunscreen active ingredients protect against EITHER UVA or UVB. This is why in broad spectrum chemical sunscreens there will usually be multiple active ingredients - some to provide UVA protection, and some to provide UVB protection.

There IS a system for measuring UVA protection, but it's not always used: this is the PA system (short for Protection Grade of UVA):

PA+ = Some UVA protection

PA++ = Moderate UVA protection

PA+++ = High UVA protection

PA++++ = Extremely High UVA protection

In short, you will always be protected from both UV rays with a physical sunscreen. With chemical sunscreen, as long as the label states "broad spectrum" you will be protected from both.

What order to put it on:

Sunscreen should always be applied LAST in your skincare routine, but before makeup. On top of moisturiser, underneath foundation (if you're wearing it).


IS entirely necessary. But it's not a time thing - it all comes down to exposure. UV rays break down the active ingredients in sunscreens, so after a certain period of exposure, you will need to top up because the ingredients will be breaking down and no longer effective. If you are going to be out in the sun with consistent exposure, a rule of thumb is reapply every 2 hours.

Repairing Existing Damage

YES, it's possible - it's just a lot more work than preventing the damage in the first place.

The following steps really do need to be taken in order - there is no point doing step 2, without first ensuring you are doing step 1. Similarly, there is no point doing step 3, if you are not already doing steps 1 and 2.


Prevent any further damage to the skin by using sun protection diligently.


Provide your skin with all of the tools it needs to repair the damage already done. Our skin has a phenomenal capacity to heal itself, and is capable of amazing things if it has what it needs to do so.

Primarily, this is going to be topical vitamin A (in a serum form) - but also:

- vitamin B

- vitamin C

- DNA repair enzymes

- melanin inhibitors

- antioxidants

And of course - ensuring your skin is well hydrated, and has good lipid content so it can function properly.


Topical care can do amazing things, but clinical treatment can take your skin the extra mile when repairing UV damage. When dealing with UV damage in clinic, we tend to focus on vitamin A infusion peels (high doses of topical vitamin A to induce cellular repair), and micro-needling (controlled tissue injury to induce cellular repair and tissue remodelling).

I hope this article has been informative, and helped you to understand the importance of protecting your skin! But please do let us know if you have further questions - and if you have UV damage that you'd like to work on repairing, book a free consultation with us to find out what you can do to improve your skin health.

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