Many people don’t consider applying SPF unless they’re on holiday, or when they know they’ll be sat in the sun for hours on end; the latter being a strong possibility now pub gardens and terrace dining is in full swing. Yet SPF should be used daily. Even in winter. Even if you’re not planning on leaving the house.   

“Sun protection is important because UV rays mutate the DNA. UVA rays can penetrate clouds, fog and glass, and [the DNA] changes from these rays hitting your skin can be lifelong,” Dr Gregory Bays Brown, founder of ReVive skincare, tells WIRED. “The sun damage one receives at age 16 stays for a lifetime.”

In fact, any tan and colouration on your skin from the sun is a sign of damage. There’s no such thing as a safe tan, other than the fake variety. 

SPF stands for Sun Protection Factor. It’s a term that refers to how well a skincare product protects you from ultraviolet rays. Light from the sun includes a broad spectrum of wavelengths, from visible light, to infrared, and ultraviolet (UV). UV light comes in three variations – UVA, UVB and UVC. Although, it’s just the first two we need to be concerned about; UVC has a short wavelength that can't penetrate the atmosphere, so doesn't reach Earth's surface.

UVB rays are what cause sunburn. They increase the risk of skin cancers by penetrating the upper layers of the skin. B for burning. UVA rays also cause skin cancer, but in the deeper layers of the skin, killing off collagen in the process. Collagen is what gives our skin a youthful appearance, which is why UVA rays are associated with the premature ageing effect the sun has on our skin. Hence, A for ageing. 

UVA rays – which are the primary ray in tanning beds – pose the bigger threat because they’re the same strength regardless of the time of day or weather. 

To protect your skin from the UV rays, sunscreens with SPF contain active ingredients called UV absorbers and UV reflectors. 

"UV absorbers are chemicals that absorb UV radiation and convert it to a very low level of heat," explains Terry Slevin from Cancer Council Western Australia (CCWA). "So low most don’t notice it, but a small proportion of people do report sunscreens make them feel uncomfortably warm." UV absorbers usually contain carbon. UV reflectors are usually oxides, such as zinc oxide or titanium dioxide, that scatter UV radiation and prevent it from reaching the skin.”

Yet with sunscreens being sold at wildly different prices, with different star-ratings, factors and in different formulas (cream, lotion, oil, mist, powder…), how do you know which gives you the best protection? 

The NHS advises that when buying sunscreen, always opt for an SPF of at least 30 to protect against UVB, and at least 4-star UVA protection. Here’s what that means: 

To guarantee you’re protecting your skin – and DNA – from the damaging effects of both UVA and UVB you need to buy a sunscreen labelled as “broad-spectrum”. 

As the name suggests, it covers a broad range of rays in the ultraviolet spectrum and for a product to call itself broad-spectrum means it conforms to regulator limits by blocking a significant proportion of UVA specifically, but also UVB. 

If the product doesn’t explicitly use the term broad-spectrum, UVA protection can also be indicated by the letters "UVA" in a circle. This indicates that it meets the EU standard.

If a product protects against UVA, it must also carry a star rating. This is sometimes shown instead as a PA rating. 

The star rating ranges from 0 to 5, and it refers to the percentage of UVA radiation absorbed by the sunscreen in comparison to UVB. In other words, the ratio between the level of protection afforded by the UVA protection, and the UVB protection. 

A low SPF, for instance, 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.

The PA rating offers a similar indication of UVA protection by using the letters PA followed by + symbols. 

• PA+ = some UVA protection
• PA++ = moderate UVA protection
• PA+++ = high UVA protection
• PA++++ = extremely high UVA protection

Next up, you need to determine what your phototype is, or how fair you are. 

“The way the skin reacts to the sun’s rays varies a great deal from person to person,” Victoria Trueman, Comfort Zone's international educator tells WIRED. Skin types are categorised on the Fitzpatrick scale, and this refers to the pigment of skin and how likely those skin types are to tan and burn. The scale is as follows: 

• Type I: always burns, never tans
• Type II: usually burns, tans a little
• Type III: sometimes burns, tans uniformly
• Type IV: rarely burns, always tans well
• Type V: very rarely burns, tans very easily
• Type VI: never burns

“At Comfort Zone, we have a Skin Analyser machine that looks deep into the skin,” says Trueman. One of the optics is an SPF evalsuation lens, which measures the skin colour degree and defines the skin phototype. From this we can recommend the best SPF product for you to use.” 

In lieu of such a machine, a good guide is to choose a SPF number at the opposite end of where you are on the scale. If your phototype is low, you’re best suited to a high SPF, for instance.  

An SPF number gives an indication to how long the sun’s UV radiation takes to redden your skin. This is determined by your skin type and then measured by how much UV light is allowed to pass through, versus how long it would take if you weren’t wearing any SPF.

For example, SPF 20 allows one-twentieth of UV to reach the skin, or 5 per cent. It blocks the other 95 per cent. On average, cream with an SPF 30 rating lets in around 3 per cent of UVB rays, while an SPF 50 cream allows 2 per cent.

While the difference between percentages may seem inconsequential, SPF 30 creams allow 50 per cent more radiation to reach your skin than SPF 50. 

If you burn within 10 minutes of being in the sun (you have fair skin on the lower end of the Fitzpatrick scale) SPF 30 would protect you for around five hours, but it may protect someone else with a higher categorised skin type for longer.

To add to this, the intensity and wavelength distribution of UVA rays varies throughout the day and depends on where you are in the world. If in doubt, always opt for the highest number available.

Best SPF products 

Sunscreen should be reapplied every couple of hours, and you should seek shade during the midday sun, and cover up when possible. Here is WIRED's pick of the best ray-banning lotions.

Labelled as SPF50+, this sun cream from La Roche-Posay actually protects around the SPF 60 mark, exceeding the European standard. 

By using a photostabilising oil contained within a blend called Mexoplex, La Roche-Posay is able to reduce the number of chemical filters used in this sun cream by 15 per cent. This results in ultra-high UVA/UVB protection that’s more suitable to sensitive skin. 

Elsewhere, it has a PA++++ (Extremely High UVA protection) rating, is water-, sweat- and sand-resistant, and has a non-greasy formula. 

Price: £17.50 | La Roche-Posay | Boots | Superdrug 

Another sunscreen that is suitable for sensitive skin, Garnier’s Ambre Solaire Ultra-hydrating sun lotion SPF 50+ provides high protection, even for very fair skin, while keeping the skin soft and hydrated for hours thanks to the addition of shea butter. 

Despite being a thick-ish cream, it absorbs quickly and offers broad-spectrum, European- and dermatologist-approved protection. 

Price: £5 | Amazon | Boots | Superdrug 

If you’re late to the SPF game, or particularly looking to prevent premature ageing, the entire Sun Soul range from Comfort Zone ticks a lot of boxes. Its Face and Body Cream is a highlight. 

In addition to high UVA and UVB protection, this SPF 50+ dry-touch cream contains peptides and antioxidants. The former protects and repairs DNA, while the latter protects from free radicals and pollution. These active ingredients work to prevent dark spots and hyperpigmentation.

Price: £23 | Amazon | Feelunique | Lookfantastic 

Boots has been a sunscreen pioneer for decades having been the research team to first develop the now ubiquitous UVA star rating in 1992, later adopted by the EU. 

The entire Soltan range offers great value for money, with maximum five-stay UVA protection, and antioxidants, but its Once range is a game changer. As the name suggests, you only need to apply this sunscreen once “provided you follow the instructions”, and it will offer protection for eight hours. The instructions include reapplying after being in water, staying out of the sun at peak times and covering up when possible. 

Price: £10 | Boots 

If the idea of adding sunscreen to your daily routine makes your oily, congested skin shudder at the thought, look for a moisturiser designed for breakouts without sacrificing on protection.  They tend not to offer the broad, highest-level protection seen on standalone sunscreens, but they’re better than not using anything at all. 

This moisturiser from Nip+Fab contains glycolic acid to brighten and clear the skin. It’s called Post-Glycolic because your skin is particularly sensitive to the sun after using the acid – and any other alpha-hydroxy acid, for that matter. Hence the addition of SPF 30.  

It's oil-free, making it lightweight and less likely to clog up your pores, and contains Witch Hazel as well as niacinamide. Both soothe and calm the skin, and reduce redness. Witch Hazel acts as an anti-inflammatory, and niacinamide provides a barrier on the skin to lock in moisture. 

£20 | Amazon | Boots | Lookfantastic

If you want to add a touch of coverage while protecting your skin from the sun, try these tinted sunscreens from EF Skin. Available in three tones – white, light and dark – the Omni Sunshine Block offers SPF 50+ protection while soothing the skin, and hydrating. It’s pricey, but is effectively a 2-in-1 product. 

£45 | EF Skin

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This article was originally published by WIRED UK