UV and Sunscreens

Many people use sunscreen incorrectly. For this reason, we thought it important that we write about the ins and outs of sunscreens (correct usage etc) so that our customers (and others) could become more informed.

Correct Sunscreen Usage: In Brief

To help people use sunscreens correctly, international authorities such as the WHO have provided recommendations. A sufficient amount of sunscreen should be applied at least 30 minutes before sun exposure. The general recommendation for sunscreen application rate is that 2mg of sunscreen should be applied per cm square of skin surface, corresponding to about 40g of sunscreen (about 1/5 of a usual sunscreen bottle @ 200g) for a full body application to achieve the labeled SPF. Care should also be taken to cover all areas of skin that will be exposed to UV.

The recommendation as to the reapplication frequency of sunscreen is that it should be reapplied every two hours to ensure you are protected from UV. This is typically good advice if you are using a high quality, accurately listed SPF 30 – 50 sunscreen. However, optimal sunscreen reapplication timing can be far more complex than this; it comes down to the quality of formulation, the reliability of the SPF stated label claim (and UVA rating), and the conditions the sunscreen is used in.

For example, factors such as sweating, how often you go into the water, and towelling off reduce the protection of sunscreens.

Other factors such as the breakdown of sunscreen minerals, or poorly formulated sunscreens can offer sufficient protection against UVB while be lacking in UVA protection (e.g. zinc oxide containing sunscreens, when formulated in conjunction with chemical UV filters, have been shown to lose greater than 80% filter protection against UVA within 2 hours)[1].

Additionally, misleading SPF and/or ‘Broad Spectrum’ listings or substandard sunscreen formulations (which are more common than many realise) can leave you wide open to sun damage.

Studies show that most people underapply sunscreen

According to the Cancer Council of Australia, “The biggest concern when it comes to sunscreen is that Australians aren’t applying it correctly and are getting sunburnt as a result. Other studies show that 85% of Australians don’t apply enough sunscreen. We also know many don’t apply sunscreen 20 minutes before heading outdoors or don’t regularly reapply every two hours.”

The SPF rating of a sunscreen is determined using a given amount of sunscreen applied per centimetre square of skin. However, studies have determined that most people use less sunscreen than is used in SPF testing, reducing the SPF that sunscreen offers in real world conditions. For example, one study found that typical amounts of SPF 50 sunscreen applied by people — less than the recommended coverage manufacturers use to determine their SPF rating — provided only a maximum of 40 percent of the expected protection from the sun’s harmful UV rays. The study further determined that protection of the skin from the harmful, UV-induced DNA damage known to underlie cancers was only significant when sunscreen was applied at a thickness between 1.3 and 2.0 milligrams per centimetre squared, whereas most people only apply, on average, 0.75 milligrams per centimetre squared. [2]

Other studies have concluded that for optimal UV protection people should apply sunscreen 30 minutes before and a second time soon after intense sun exposure.

For example, one study concluded that sunscreen users should apply sunscreen liberally to exposed sites 15 to 30 minutes before going out into the sun, followed by reapplication of sunscreen to exposed sites 15 to 30 minutes after sun exposure begins. Further, reapplication is necessary after vigorous activity that could remove sunscreen, such as swimming, towelling, or excessive sweating and rubbing.[3]

Often People do Not Follow Sunscreen Recommendations

Studies have found that many people fail to follow the health recommendations on sunscreen reapplication. One 2019 study, which surveyed 30,000 people, found that overall 79.4% of the respondents wore sunscreen always, often or sometimes when being exposed to the sun. However, 87.2% of sunscreen users did not follow the recommendations on timing of reapplication.[4]

Misleading SPF Label Claims

In some cases, the SPF listed on sunscreens can be overstated, leading you to think you are more protected than you are. For example, a 2016 report examined seven mineral sunscreen products. Package labels reported SPF values of 30 to 50+. Two of seven products met the labelled SPF value, whereas the remaining five offered only 16 percent to 50 percent of the advertised SPF. In another study by Consumer Reports that analysed the SPF ratings on 20 sunscreens it was found only two products met their SPF claims. One product tested at half its claim and the rest of the sunscreens tested at 4%-40% below their SPF claims

In 2020, the Consumer Council of Hong Kong found that 80% of 30 sunscreens tested did not meet their SPF claims. SPF test results revealed only 4 sunscreen products, of 30, labelled with high protection (SPF30 to SPF50) met their SPF claims. 1 product labelled as SPF30 had the largest discrepancy with its measured SPF value of only 9.8. According to the council, some of the brands that fell short were Fancl, Shiseido Anessa, Curel, Estee Lauder and Bio-essence.

In another instance, a very popular brand sunscreen, Purito Centella Green Level Unscented Sun, also known as “the Internet’s Favourite Sunscreen”, which had an SPF rating of 50, was independently tested through two European laboratories and it was found to have under half its claimed SPF 50, coming in at just SPF 19.  Naturally, being the Internet’s Favourite Sunscreen, news of this spread rapidly – the “Purito Gate” controversy – and a consumer backlash against the company behind the product ensued. This triggered further controversy surrounding Korean sunscreen products and several other popular Korean brands were also found to have overstated SPF claims. The fallout from this, among other things, resulted in several Korean brands being pulled from shelves in numerous countries and at the extreme end of things, Australia, which has the strictest sunscreen regulations in the world, banning the sale of Korean made sunscreens.

In yet another case, in 2022, Consumer NZ found 7 out of 8 sunscreens they tested failed to live up to their SPF claims. While the 7 sunscreens provided high SPF protection (SPF30 or higher) they didn’t meet their very high protection (SPF50+) label claims. Prior to this, in 2019, Consumer NZ had found that 9 out of 20 sunscreens they tested failed to meet their SPF claims, with another 3 of the products meeting their SPF claim but falling short on ‘broad spectrum protection’.

Many who read this information might be shocked by just how common it is that sunscreens – including reputable big name brands – don’t meet their labelled SPF claims. However, when one understands the regulations and compliance enforcement, on a country to country basis around sunscreens, it is perhaps not too surprising that so many products come up short when independently tested.

In fact, information from multiple countries as to multiple brands of sunscreens not meeting their SPF claims is widely available across the internet. For example, in June 2022, ‘Which?’ an independent UK based consumer group tested five mineral sunscreens. All the mineral-based products failed SPF or UVA tests, and several products failed on both. Four SPF 30 mineral-based sunscreens from Alba Botanica, Clinique, Hawaiian Tropic and Tropic Skincare – costing between £11.99 and £28 – didn’t come close to providing the protection they claimed. A fifth product – Green People Scent Free Sun Cream SPF 30, which uses mineral and chemical UV filters, failed to protect adequately from UVA. A £26 product from Clinique was the worst performer, barely giving 1/3 of the protection it claimed.

While it is hopefully the exception rather than the norm, it is therefore important to understand that some sunscreen products have overstated SPF and/or broad-spectrum claims.

Broad Spectrum Protection

UV exposure has a complicated relationship to skin cancer risk. In the past it was believed that UVB was primarily responsible for skin cancer. However, recent research has shown that both UVB and UVA contribute to skin cancer. Further, UVA which penetrates the skin more deeply than UVB, is largely responsible for photoaging (premature damage/aging of the skin).

The SPF rating of a sunscreen only applies to UVB protection. It indicates nothing about UVA protection.

Due to this, in addition to a product labels SPF, you may also see a UVA rating on a sunscreen. However, in the field of UVA protection, the labelling on sunscreens can be extremely confusing. Each country has its own way of labelling and testing protection against UVA.  These being UVA-PF (Europe), PA (Asia), Broad Spectrum (US) and Boots Star Ratings (Britain). Non-uniform labelling leads to consumer confusion and, consequently, a greater chance of manufacturers misleading consumers with incorrect indications on their sunscreens. Additionally, as standards are not uniform, some countries standards are superior to others. That is, not all sunscreen labels are created equal. For example, European standards set a far higher bar for UVA protection than U.S. standards.[5]

The outcome of this?

In a 2017 study, researchers tested 20 U.S. sold sunscreens. Two in vitro UVA protection tests were conducted in accordance with the 2011 US FDA standards. The study concluded, the majority of tested sunscreens offered adequate UVA protection according to US FDA guidelines for broad-spectrum status, but almost half of the sunscreens tested did not pass standards set in the European Union.

In a similar 2021 study, 51 sunscreen products for sale in the United States, with SPF values from 15 to 110 and labelled as providing broad-spectrum protection, were tested. The majority of products provided significantly lower UVA protection with the average unweighted UVA protection factor just 24 percent of the labelled SPF. Just 18 of 51 products passed the UVA protection test required of products sold in Europe. [6] Given these findings, consumers should assume many sunscreen products sold in the U.S. offer lower balanced UVA/UVB protection than might be expected.

Sunscreen Application Tips

Apply sunscreen 20 – 30 minutes prior to going outdoors into direct, intense sunlight

Reapply sunscreen every two hours.

Use sunscreen of SPF 30 or higher when going outside.

Make sure sunscreen is labelled “broad spectrum,” which means it protects against UVA and UVB rays. Because skin aging is caused by both UVB and UVA be sure that besides having a high SPF rating (which only relates to UVB protection), the sunscreen also has a high UVA protection rating.

Check the expiration date of your sunscreen to make sure it still has its full efficacy.

Apply sunscreen to all exposed skin areas

Apply adequate amounts of sunscreen to sun exposed skin: Most people (75 – 85 % dependent on study) underapply sunscreen. The SPF rating of a sunscreen is determined using a given amount of sunscreen applied per centimetre square (cm²) of skin. However, studies have determined that most people use less sunscreen than is used in SPF testing, reducing the SPF that sunscreen offers in real world conditions. Sunscreen should be applied at about 2mg/cm² – e.g. for an average adult, use about enough to fill a shot glass to cover exposed skin at the beach.

References 

[1] Ginzburg AL, Blackburn RS, Santillan C, Truong L, Tanguay RL, Hutchison JE. Zinc oxide-induced changes to sunscreen ingredient efficacy and toxicity under UV irradiation. Photochem Photobiol Sci. 2021 Oct;20(10):1273-1285.

[2] Young AR, Greenaway J, Harrison GI, Lawrence KP, Sarkany R, Douki T, Boyer F, Josse G, Questel E, Monteil C, Rossi AB. Sub-optimal Application of a High SPF Sunscreen Prevents Epidermal DNA Damage in Vivo. Acta Derm Venereol. 2018 Oct 10;98(9):880-887. doi: 10.2340/00015555-2992. PMID: 29944164.

[3] Diffey BL. When should sunscreen be reapplied? J Am Acad Dermatol. 2001 Dec;45(6):882-5. doi: 10.1067/mjd.2001.117385. PMID: 11712033.

[4] Görig T, Schneider S, Seuffert S, Greinert R, Diehl K. Does sunscreen use comply with official recommendations? Results of a nationwide survey in Germany. J Eur Acad Dermatol Venereol. 2020 May;34(5):1112-1117. doi: 10.1111/jdv.16100. Epub 2019 Dec 12. PMID: 31746063.

[5] Wang SQ, Xu H, Stanfield JW, Osterwalder U, Herzog B. Comparison of ultraviolet A light protection standards in the United States and European Union through in vitro measurements of commercially available sunscreens. J Am Acad Dermatol. 2017 Jul;77(1):42-47. doi: 10.1016/j.jaad.2017.01.017. Epub 2017 Feb 24. PMID: 28238452.

[6] Andrews DQ, Rauhe K, Burns C, Spilman E, Temkin AM, Perrone-Gray S, Naidenko OV, Leiba N. Laboratory testing of sunscreens on the US market finds lower in vitro SPF values than on labels and even less UVA protection. Photodermatol Photoimmunol Photomed. 2022 May;38(3):224-232. doi: 10.1111/phpp.12738. Epub 2021 Oct 19. PMID: 34601762; PMCID: PMC9298345.