Understanding Sunscreen - Part 1

Decoding Sunscreen & Debunking Myths

Flowers in sunlight.


Have you ever wondered about whether the SPF in your moisturiser is enough to protect you against sun damage?

Do you wear sunscreen religiously, occasionally, or just when the sun is hot?

Do you know what to look for on the label?

And what do all those numbers & symbols actually mean?

All this & more in Part 1 of our Investigating Sunscreen Blog.

Update 2021: This blog was written & published in May 2020. Much of the content remains relevant, although as the UK has now left the EU, there are now separate laws governing UK cosmetics.


- Why it’s Important
- Defining Sunscreen – What is it? What is it not?
Decoded: UV, UVA, The Star Rating, UVB, SPF, Broad Spectrum & more
- How should we use it?
- Debunking the Myths:
MYTH: I don’t burn, so I don’t need sun protection
MYTH: SPF in my moisturiser is enough *updated April 2021
MYTH: I only need Sunscreen when I go abroad
MYTH: I only need Sunscreen when I’m outside
MYTH: Sunscreen stops me getting Vitamin D
MYTH: Sunbeds are safe
- A final word


Infographic, how to read a sunscreen label

Decoding Sunscreen and Debunking Myths


First, a brief introduction as to why I'm researching sunscreens.

In my facials clinic here in Somerset, I see skin close-up & hear a lot of concerns about visible signs of ageing & sun damage such as pigmentation, wrinkles & sagging skin. Customers are also more & more interested in the ingredients in their skincare products.

I’m often asked about how to minimise signs of ageing & invariably the topic of sunscreen is part of the conversation. Many people consider an SPF in their daily moisturiser is enough, but, as we will see, this isn’t the case. Bottom line - there's no point spending a fortune on skincare if you're not doing the one thing that helps prevent signs of ageing more than anything else - protecting your skin from harmful UV light. Not to mention protecting yourself from serious disease. 

As a “Type 01” in the “Skindex” (more on this later), I personally have always been vulnerable to UV light. Into middle age, I am now developing pigmentation & actinic (solar) keratoses: “rough patches of skin caused by damage from years of sun exposure”[1] (NHS UK) which have led to visits to a Dermatologist through the NHS. Some of these patches have been treated with gels, some removed. These patches haven’t developed as a result of sunbathing, as growing up I was always covered with hat, sleeves, sunscreen & not encouraged to lie in the sun. I have, like many of us, been caught out & ended up burning several times in my life – falling asleep in the “shade”, bodyboarding in the sea on a cloudy day. So I’m well aware that I’m high on the risk list & that I routinely need sun protection.

But choosing a sunscreen can be so confusing for consumers. With the terminology - SPF, UVA, UVB, the star rating, broad-spectrum… how do you know what to choose? Does the label make any sense? And then there are the different types of sunscreen – “Chemical” & Organic, “Physical” or “Mineral & Inorganic and in more recent years, Nano versions of these. Next, environmental concerns & health concerns about the ingredients or even the packaging. And the marketing - Water-resistant, Reef friendly, for Kids, for Face, for Body… How do you know where to start? And what about Vitamin D?

I’ve set out to try & demystify sunscreens & to help make it easier for you to choose. I’m neither a doctor nor a dermatologist – so I have researched online through reputable sites such as the British Association of Dermatologists (BAD), the NHS, Cancer charities & the sunscreen brands themselves. I’ve referred to EU Cosmetic Legislation, tapped into industry resources & studied scientific papers. I’ve also made direct communication with brands & marine charities, to get their take on environmental & health concerns. More on that in Part 2

Defining Sunscreen – What is it? What is it not?

 “Sunscreen products protect against UV radiation. They are cosmetics according to Regulation (EC) No 1223/2009. The efficacy of sunscreen products, and the basis on which this efficacy is claimed are important public health-issues.”[2] (European Commission)

“The Cosmetics Regulation requires that any claim made by a product must be substantiated; and SPF (Sun Protection Factor) numbers, UVA protection, ‘water resistant’ or a durability claim on a sunscreen product are to be considered product claims.” [3] Cosmetic, Toiletry & Perfumery Association (CPTA)

Professional Sunscreen does:

  • Protect against a high % of Ultraviolet (UVA & UVB) radiation
  • Help protect against the development of skin cancer
  • Help protect against accelerated signs of ageing such as pigmentation, wrinkles & ‘leathery’ texture

Sunscreen is not:

  • Simply an SPF in your face cream, or in your make-up.
  • A complete sunblock  
  • Waterproof
  • An alternative to other forms of protection: “Sunscreens should not be used as an alternative to clothing and shade, rather they offer additional protection.”[4] (British Association of Dermatologists)
  • A once-only application

The unequivocal advice from doctors & dermatologists is that it’s vital to wear sunscreen to protect from UVA & UVB rays & hence, from the risk of developing skin cancer, which is on the rise.

“Not everyone who is over-exposed to UV will develop skin cancer, but thousands of people in the UK do every single year.”[5](Public Health Matters)

The World Health Organisation states that the increased diagnosis of skin cancers is down to “altered behaviour rather than ozone depletion. More outdoor activities and altered sunbathing habits often result in excessive UV exposure.” [6] (World Health Organization)

In an article appearing on the BBC online in 2019[7] Richard Weller, honorary consultant dermatologist at the University of Edinburgh, is quoted as saying:

“Any conversation on sunscreen must start with acknowledging that there is robust evidence that it prevents skin cancer.”

In other words, you must understand the dangers of developing skin cancer if you are to take sunscreen seriously. Interestingly, it’s often the worry about appearance & visible signs of ageing which motivates people to use a sunscreen. (I haven’t discussed skin cancer in-depth in the article but there are plenty of resources online to explain the different forms it can take).

So, given that you believe in the need to wear sunscreen, how on earth do you choose from the confusing array of products available?

One of the main considerations for most people is obviously their budget. More expensive doesn’t necessarily mean more effective. The texture is important, too, as you’ll only use it if you like the feel & the scent, it’s easy to rub in & your skin feels good with it on. Then there’s the question of formulation. Does it have other ingredients in it, such as antioxidants & vitamins, to condition & nourish your skin? Or are you happy with a simple sunscreen – just the actual UV filters & the technical stuff to make it work? We’ll discuss all of these issues in Part 2. But for now, the first consideration is understanding the different levels of protection & how/when to use it.

Decoded: UV, UVA, The Star Rating, UVB, SPF, Broad Spectrum & more


UV stands for “Ultraviolet”. This type of light, or radiation, was discovered in 1801. There are 3 types of UV rays – UVA, UVB & UVC categorised by their wavelength. It is the UVA & UVB rays that reach us here on earth, while the most dangerous rays, UVC, are “almost completely absorbed by our atmosphere” according to NASA. [8]

Ultraviolet light is invisible to human beings (apart from rare exceptions[9].)

“Ultraviolet (UV) light has shorter wavelengths than visible light. Although UV waves are invisible to the human eye, some insects, such as bumblebees, can see them. This is similar to how a dog can hear the sound of a whistle just outside the hearing range of humans.” (NASA)


UVA is long wavelength, penetrating deep into the dermis (the living tissues of “true” skin underneath the epidermis (the outermost layer of skin))[10]. The detrimental effects are well documented:

“UV irradiation in the form of UVA is associated with skin ageing. UVA affects the elastin in the skin and leads to wrinkles and sun-induced skin ageing (for example coarse wrinkles, leathery skin and brown pigmentation), as well as skin cancer. UVA can penetrate window glass and penetrates the skin more deeply than UVB. UVA protection in a sunscreen will help defend the skin against photo ageing and potentially skin cancer.”[11] (British Association of Dermatologists)

So, as well as using UV protection outside, you may also need to protect yourself if you are exposed to sunlight through a standard glass window, which won’t block a substantial amount of UVA: “Ordinary glass absorbs 97 per cent of the UVB rays that cause sunburn and some skin cancers, and 37 per cent of the less harmful UVA radiation.”[12] (Science Focus)

To ensure you are protected from UVA light, when choosing a sunscreen made in the EU, look for the standardised logo (above). This shows that the product has passed the necessary tests & indicates to the consumer that:

the UVA protection is at least a third of the SPF value and meets EU recommendations.” [13] (NHS UK)

The star rating

The UVA content of a sunscreen may also be indicated by a star rating (a line of stars on the packaging ranging from 3-5). This can be a confusing rating for the consumer, as it isn’t industry-wide.

The star rating is a proprietary method introduced by Boots in 1992[14] & was the first rating for UVA in Europe. You’ll find that some other brands are licensed to use this also. So what does it mean?

The number of stars indicates the ratio between the levels of UVA & UVB protection in the product. So it’s important to understand the following, explained by the British Association of Dermatologists:

Be aware that if you choose a low SPF it may still have a high level of stars, not because it is providing lots of UVA protection, but because the ratio between the UVA and UVB protection is about the same. That’s why it’s important to choose a high SPF as well as a high UVA protection (e.g. a high number of stars). Sunscreens that offer both UVA and UVB protection are sometimes called ‘broad spectrum’. A sunscreen with an SPF of 30 and a UVA rating of 4 or 5 stars is generally considered as a good standard of sun protection in addition to shade and clothing.”[15] (British Association of Dermatologists)


UVB is medium wavelength, primarily causing damage on the epidermis. It causes sunburn & has a strong link to cancer:

“UVB is the form of UV irradiation most responsible for sunburn and has strong links to malignant melanoma and basal cell carcinoma risk (types of skin cancer). A sunscreen with a high SPF (sun protection factor) will help block UVB rays and prevent the skin from burning, and by extension damage that can cause skin cancer.”[16] (British Association of Dermatologists)

UVB also promotes the production of Vitamin D in the body, which is important for human health. More on that later.


The SPF (Sun Protection Factor) rating indicates how long the sunscreen is designed to protect you from the effects of UVB light which, in simplistic terms, causes burning. An international standardised test determines a product’s SPF.

Do this simple calculation: multiply the time it takes your skin to redden in the sun (e.g. 10 minutes) with the SPF number (e.g. SPF30) to have a guideline for how long the SPF is designed to protect you from UVB when used exactly as directed (e.g. 10 x 30 = 300 minutes). Don’t, however, take this at face value. Many factors will affect the effectiveness of the SPF, including how sun-sensitive your skin is, the strength of the UV light, any reflection from the environment, how well you have applied the product, whether you have rubbed the product off or been swimming and so on. Dermatologists advise reapplying sunscreen at least every 2 hours*[17] (British Association of Dermatologists)

& the advice from the NHS is “Do not spend any longer in the sun than you would without sunscreen.”[18]

When choosing your sunscreen dermatologists recommend SPF30 or 50.[19] (Independent)

The difference between the level of protection you receive from UVB light via SPF30 and SPF50 is minimal, around 1%. SPF30 lets about 3% of UVB rays in while SPF50 lets about 2% in.[20] (Skin Cancer org) Some sunscreens boast higher than SPF50 (you may see a + sign e.g. SPF50+) but again the difference is marginal. The European Commission recommendation states that “sun protection factors above 50 do not substantially increase the protection from UV radiation.” [21](European Commission)

In addition to the SPF, the product should display one out of four categories of protection: ‘low’, ‘medium’, ‘high’ and ‘very high’.[22] (European Commission)

Whatever the SPF factor, the sunscreen is only going to be as effective as the way it is used & the SPF shouldn’t ever be used as a way to maximise skin exposure when wearing the product.  

Broad Spectrum

Broad Spectrum, which you sometimes see on packaging, simply means that your sunscreen protects you from both UVA & UVB (as opposed to, for example, a moisturiser which contains only SPF).  

And the rest…

The EU requires any product claiming “water-resistant” or “water repellent” to be substantiated through testing. No sunscreen is fully waterproof. The EU ‘best practice’ guidelines state:

“The principle of the water resistance test is to compare the Sun Protection Factor for a sunscreen product after a period of immersion in water with the original, static SPF of the product determined according to the International Sun Protection Factor (SPF) Test Method.” [23] (Cosmetics Europe)

When using a water-resistant sunscreen, it is important to remember that it is only as efficient as the way you apply it & shouldn’t be used as an excuse to stay in the water for longer. Special care is needed:

“up to 85 percent of a product can be removed by towel drying, so you should reapply after swimming, sweating, or any other vigorous or abrasive activity.”[24] (British Association of Dermatologists)

You may also see products that claim extra durability, such as 'extended wear' or 'once a day', but it is actually prohibited by law in the EU to suggest a sunscreen product doesn’t need re-application.[25] The British Association of Dermatologists explains that human beings don’t replicate the conditions of a sunscreen test & it is too easy to miss a crucial area when applying – recommending that all sunscreens are reapplied “liberally every couple of hours[26] (British Association of Dermatologists) including those designed to last longer.

For the consumer, other particular areas of interest in relation to the sunscreen label in the EU are:

  • The list of ingredients in descending order of weight & any allergens (these are called International Nomenclature of Cosmetic Ingredients (INCI) names & are internationally recognised) Some products may also add the common names to help you decipher the label.
  • The Expiry date of the product or, if it will last longer than 30 months from manufacture, a “Period after Opening” which is shown as an “open jar” symbol with a figure inside e.g. 12M meaning that it will be effective for 12 months after opening, if stored according to instructions
  • Warnings & clear instructions for use

How should we use sunscreen?

First up, make sure the sunscreen is not past its expiry date & is stored correctly. If it looks, feels or smells odd, don’t use it if you suspect it has gone off.

Use it in conjunction with sun safety advice. From the NHS[27]:

  • “Spend time in the shade when the sun is strongest. In the UK, this is between 11am and 3pm from March to October.
  • make sure you never burn
  • cover up with suitable clothing and sunglasses
  • take extra care with children
  • use at least factor 30 sunscreen”

Also, do be aware that if you have recently used retinol products or acids then your skin will be more vulnerable than usual to UV light.

People often ask when you should apply your sunscreen if you are using other products, too. There is conflicting advice online, so I went to the British Skin Foundation website for the definitive answer:

“moisturise first, then apply sunscreen afterwards followed by make-up if you choose.”[28] (British Skin Foundation)

It may be wise, if you are using a moisturiser beforehand, to allow it to sink in before applying your sunscreen on top.

Your sunscreen is only going to work as intended if it is used as directed. Most people don’t apply enough sunscreen & also forget areas such as tops of ears, eyelids, backs of hands. So apply thoroughly to areas that will be exposed before exposing your skin to UV light, which allows it to “sit into the skin”.[29] (BBC)

The British Association of Dermatologists advice is this:

“Apply sunscreen 15 to 30 minutes before going out in the sun to allow it to dry, and then again shortly after heading outdoors to cover any missed patches and to make sure you're wearing a sufficient layer.”[30] (British Association of Dermatologists)

The NHS recommends that “If you plan to be out in the sun long enough to risk burning, sunscreen needs to be applied twice: 30 minutes before going out & just before going out.” (NHS UK)

It's also recommended by the NHS to “reapply sunscreen every 2 hours, as the sun can dry it off your skin.”[31]

Apply sunscreen liberally. “When using lotions, as the bare minimum you should to apply at least six full teaspoons (approximately 36 grams) to cover the body of an average adult, which is more than half a teaspoon of sunscreen to each arm and the face/neck (including ears), and just over one teaspoon to each leg, front of body and back of body.”[32] (British Association of Dermatologists)

A good tip is to rub in the direction of your hair growth to help absorb more quickly, especially with mineral sunscreens which may be harder to rub in.[33] (BBC)

To understand more about the usage & labelling instructions required in the EU for a sunscreen product, there is a clear document published by Cosmetics Europe, the European Trade Association who represents “the interest of the cosmetic, toiletry & perfumery industry.”[34](Cosmetics Europe)

Debunking the Myths:

MYTH: I don’t burn, so I don’t need sun protection

We need sun protection from birth. It is recommended by the NHS that children under the age of 6 months should not be exposed to “direct strong sunlight”[35] (NHS UK) & that “From March to October in the UK, children should:

  • cover up with suitable clothing
  • spend time in the shade, particularly from 11am to 3pm
  • wear at least SPF30 sunscreen
  • Apply sunscreen to areas not protected by clothing, such as the face, ears, feet and backs of hands.”

According to research undertaken at Birmingham university, it’s not just young children, but adolescents too who must take care:

“Ecological studies demonstrate that sun exposure during early life, especially childhood and adolescence, is a strong determinant of future risk of melanoma, suggesting that the skin at this age is at increased susceptibility to the carcinogenic effects of ultraviolet radiation.” [36] (Birmingham University)

While some skin types are more at risk from developing skin cancer from exposure to UV light than others, “everyone is at risk” [37] according to the British Skin Foundation. The National Cancer Institute in the US reiterates:

Although dark skin does not burn in the sun as easily as fair skin, everyone is at risk for skin cancer. Even people who don't burn are at risk for skin cancer. It doesn't matter whether you consider your skin light, dark, or somewhere in between. You are at risk for skin cancer. Being in the sun can damage your skin.“[38](The National Cancer Institute)

How much protection we need varies, depending on your skin type & other risk factors. The British Association of Dermatologists publishes a skin type guide to help you understand your own skin:

“Recommendations regarding sun protection (e.g. clothing, shade and sunscreen) should be used in conjunction with the skin type guide. For example, the use of clothing and sunscreen applies to skin types I and II at all times in the sun, and to skin types V and VI during periods of prolonged or intense sun exposure.”[39]

SKINDEX from British Association of Dermatologists

Type 01: Pale skin, burns very easily and rarely tans. Generally have light coloured or red hair and freckles.

Type 02: Fair skin that usually burns, but may gradually tan. Some may have dark hair but still have fair skin.

Type 03: Skin that burns with long or intense exposure to the sun but generally tans quite easily. Type 04: Olive-coloured skin that tans easily, but could possibly burn with lengthy exposures to intense sunshine. Usually have brown eyes and dark hair.

Type 05: Naturally brown skin, with brown eyes and dark hair. Skin darkens easily with sun exposure and only burns with excessive exposure to the sun.

Type 06: Black skin with dark brown eyes and black hair. Skin very easily darkens on exposure to sun and would very rarely, if ever, burn.[40] (British Association of Dermatologists)

In 2019, the USA Skin Cancer Foundation published an article with American Dermatologist, Andrew Alexis, MD, MPH entitled “Is There a Skin Cancer Crisis in People of Colour?”[41] (Skin Cancer Org) which highlights the need for awareness across all ethnicities. 

So, yes, everyone needs sun protection, to different degrees.

MYTH: SPF in my moisturiser is enough*

*Updated April 2021, after a journalist friend mentioned that many SPF moisturisers do give broad spectrum protection - the advice is to check with the manufacturer if you are unsure.

    As we’ve seen, SPF only protects from one form of UV light – UVB. So, while you may have SPF in your face cream, for example, that may not be enough to protect you fully unless it is broad spectrum. Furthermore, how often do you reapply your moisturiser during the day?

    Check with the manufacturer to make sure that the SPF in your moisturiser is enough to protect you from both UVA & UVB light. 

    MYTH: I only need Sunscreen when I go abroad

    In the UK, the sun's UV rays are the strongest “when the sun is highest in the sky between 11am and 3pm, from early April to late September.”[42](Cancer Research UK)

    But Ultraviolet (UV) radiation from sunlight can be high, even on cloudy days, so it’s important not to be complacent with protection. But how do you know when UV levels are potentially dangerous? The Met Office forecasts the strength of UV all over the world in over 400 countries:

    “Our UV index forecast identifies the strength of the ultraviolet (UV) radiation from the sun at a particular place on a particular day, allowing you to take the necessary precautions to help reduce the impact of UV on your health.”[43] (Met Office)

    “In the UK, the sun's UV rays are the strongest when the sun is highest in the sky between 11am and 3pm, from early April to late September.” [44] (Cancer Research UK) So during these hours, when the UV index is 3 or higher, especially if you have fair skin or burn easily, it is recommended that you stay in the shade & cover up, according to Cancer Research UK. This is also recommended by Dr Walayat Hussain, British Association of Dermatologists, according to Patient Info:[45]"If the UV index is three or higher, you should be protecting your skin."[46] (Patient Info)

    So, rather than judging your need for protection simply by the brightness of the sunshine or the temperature, become used to checking the UV index daily if you plan to be outside. As I sit & write this, the sky is virtually covered with cloud, there are bright intervals but it is no means “sunny”. The Met Office tells me there is a moderate risk at level 4 and that I should seek shade during midday hours, cover up & wear sunscreen.  

    So no, sunscreen is not just for summer.

    MYTH: I only need Sunscreen when I’m outside

    As we saw in the section about UVA light, UV rays can reach us if we are seated behind glass, for example, next to a window at home or in a car* or a plane.

    *a laminated windscreen may protect you, but it’s likely the side window doesn’t[47](BBC)

    MYTH: Sunscreen stops me getting Vitamin D

    In the UK we get most of our vitamin D from exposure to UVB rays from sunlight, from around late March/early April to the end of September. To synthesise Vitamin D in this way, we need to be outside.[48] (Science Focus). Vitamin D may also be taken as a supplement & exists in some foods.

    “Vitamin D helps regulate the amount of calcium and phosphate in the body. These nutrients are needed to keep bones, teeth and muscles healthy.”[49] (NHS UK)

    So if we are covered in SPF, how do we get our Vitamin D?

    The NHS states that we need to “strike a balance”[50] (NHS UK) between protecting ourselves from the sun & getting enough vitamin D from sunlight. But what does that actually mean?

    The British Association of Dermatologists explains: “Environmental, physical and personal factors influence risk/benefit of sunlight exposure. In white-skinned people, casual short sun exposures a few times per week, taking particular care not to burn and avoiding deliberate tanning, can help provide the benefits of vitamin D while minimising risks.”[51](British Association of Dermatologists)

    The British Journal of Dermatology[52] has also published studies “which concluded that sunscreen application does not prevent vitamin D production in the majority of people[53].

    The National Institute for Health & Care Excellence (NICE) states that while “In winter months, the UK population relies on body stores and dietary sources to maintain vitamin D levels”[54]while “the best estimates suggest that for most people, everyday casual exposure to sunlight is enough to produce vitamin D in the summer months.”[55]

    So it seems that by protecting ourselves from UVB light, we won’t miss out on Vitamin D, as we’ll get enough from incidental exposure during the summer months.

    MYTH: Sunbeds are safe

    It is illegal for under 18’s to use sunbeds in the UK & for good reason. They often give out more UV light than tropical sun.[56] (NHS UK) The British Photodermatology Group and British Association of Dermatologists Consensus state:

    “There is strong evidence that use of sunbeds increases the risk of skin cancers, including malignant melanoma. For those who start using sunbeds before the age of 35 years the relative risk of malignant melanoma almost doubles.”[57]

    People misguidedly use sunbeds for “beauty” but actually, as well as heightening your risk of disease

    “They can cause your skin to age prematurely, making it look coarse, leathery and wrinkled.”[58] (NHS UK)

    So, in other words, please, just don’t. Sunbeds are not safe. Not only is your risk of cancer increased but you will age faster.

    A final word

    So there it is. What sunscreens are, what they do & what they don’t do. How & when to use them. What to refer to on the label to get the right protection for you.

    In Part 2, we look at ingredients in more detail including the different types of filter, physical & chemical, along with concerns about the environment & human health.

    Have Your Say

    Did you enjoy the read? Have we delved into all the important questions? Is there something you disagree with? Or do you have something to add? What are your thoughts? Please let us know in the comments or via email using the contact form. We'd love to hear from you.


    There are over 50 references to accompany this article. If you're interested, do get in touch.

    All opinions are my own & there are no affiliate links. Information provided by this blog is subject to change. We recommend that you do not take any information held within as a definitive guide to the matter being discussed. You are advised to seek legal or professional advice where necessary rather than relying on the content supplied by the author.

    Lucy Stevens, May 2020.  

    Thoughts? Questions? Chat with us, leave a comment.

    Comments are approved before they are published