The Analysis of Sunscreen: How It Works And The SPF System

When it comes to sun protection or something that prevents skin cancer in the long run, the first thing that comes to mind is probably sunscreen.¹Sunscreen can help protect from skin damage by reflecting, absorbing, and/or scattering the UV radiation².They are also able to delay sunburns and reduce UV-induced skin lesions.³

Some people may choose to apply sunscreen in substantial amounts multiple times every day throughout a lifetime, because they can be found in cosmetic products.²

It’s a very well-known fact that the ultraviolet rays from the sun can cause long-term, adverse effects on the skin. Hence, constant exposure to UV radiation can overwhelm the body’s defenses and cause photodamaged skin. Therefore, sunscreen is a crucial aspect; after all, it can protect your skin from the adverse effects of ultraviolet light.

Sunscreen also has something called the SPF (Sun Protector Factor) system. To know what the SPF entails, let us recap on how sunscreen works.

How sunscreen works

Sunscreens usually consist of chemical (organic) or physical (inorganic) compounds, which prevent UV radiation from penetrating the skin.⁴ Generally, UV light comes in three forms: ultraviolet A, ultraviolet B, and ultraviolet C. All of them differ in terms of wavelength.⁴

The shorter the wavelength, the higher the chances of the light radiation to cause damage biologically. The photoprotective agents, such as oxybenzone, avobenzone, octocrylene, and ecamsule, are effective against ultraviolet A and ultraviolet B.

While ultraviolet C is the most dangerous type of ultraviolet light due to its shortest wavelength, it’s not a risk because ultraviolet C cannot penetrate the earth’s atmosphere and the ozone layer usually absorbs it. Therefore, it’s not a risk to humans.

The photoprotective agents act as filters for the other types of ultraviolet light. They absorb the intense ultraviolet radiation, which causes the radiation to convert into higher energy states. When the molecules revert to the lowest energy state, the absorbed energy is converted into a lower energy wavelength, such as infrared.

Consequently, sunscreen is a popular sun-protection method, and this protection is directly proportional to the sun-protection factor (SPF).

What is sun protection factor (SPF)?

The SPF indicates the ability of a sunscreen to slow down solar radiation, which can cause a skin erythemal reaction.³The effectiveness of sunscreen agents depends on SPF and substantivity.⁵SPF mainly protects from ultraviolet B, so you can think of SPF as a measurement of UVB protection. (Note: Not all sunscreens can protect against ultraviolet A.)

SPF is measured as the ratio of the UV radiation needed to burn the skin protected by the sunscreen to that needed to burn the skin without any sunscreen.⁵ All other factors are presumed to remain constant.

SPF is measured using the following formula:

SPF = MED of protected skin/MED of unprotected skin

(MED = minimal erythemal dose)

Hypothetically, this means that products with higher SPFs would provide better protection against hazardous ultraviolet light compared to those with lower SPFs.

What SPF should I use?

As mentioned previously, the higher the SPF, the higher the protection against ultraviolet light. For instance, SPF 15 will block about 93 per cent of ultraviolet B rays, and SPF 30 blocks about 97 per cent of ultraviolet B rays. When going out, it’s recommended to put on sunblock with an SPF of 30 or higher.

It’s essential to apply enough sunscreen to any skin area exposed whenever you go out. If you are going outdoors for an extended time, such as going to the beach or pool, it’s recommended to put sunscreen that has a base SPF of 30 for half an hour before leaving and recoating every two hours.

Should you be doing water-based activities such as swimming, a good rule of thumb is to use sunscreen every time you exit the pool.

A crucial point to remember is that no sunscreen can give total protection against the sun, so you must take measures yourself. Some actions may include regular sunscreen application during the day, wearing protective clothing such as hats, and seeking shade if possible.

Do people with dark skin tones need to use sunscreen?

Short answer, yes. Long answer, just because people with darker skin tones have more melanin does not mean that they do not have a risk of developing skin cancer. They are also at risk of photoaging and are suspectable to pigmentary disorders that can be worsened by ultraviolet exposure.⁶

More importantly, the most common conditions that require people with darker skin tones to consult a dermatologist in Singapore are photo-exacerbated pigmentary disorders.⁶

Studies have revealed that cosmetic elegance is the most prioritised feature in sunscreen. People with darker skin tones have expressed that the white residue left on their skin is undesirable. This has affected the regular usage of sunscreen.⁶

Important note about SPF

SPF is only a measure of how well they can protect against ultraviolet B. It doesn’t tell you anything about how well it can protect from UVA rays. This is because ultraviolet B mainly causes photodamaged skin, such as sunburn.⁷

On the other hand, UVA deals oxidative damage to DNA and breaks down collagen fibers, causing the skin to age. Hence, while most sunscreens protect from sunburn, they do not necessarily protect from ageing skin caused by UVA.⁷

To find a sunscreen that can protect from both ultraviolet A and ultraviolet B, it’s best to find products with the label “broad spectrum”, which indicates they are good against both types of ultraviolet lights.

Do not let ultraviolet rays ruin your perfect skin

Since absorbing ultraviolet rays is inevitable in everyday life, the best thing to do is to choose a sunscreen with a good SPF factor. However, even sunscreen can only do so much, because they do not protect against ultraviolet A, unless it’s labelled as “broad spectrum”.

At Angeline Yong Dermatology, we completely understand and care for those in need of a treatment that can protect against photodamaged skin. Starting from mole checks all the way to performing mohs micrographic surgery, we constantly strive to deliver personally designed solutions that are best suited for your skin, leaving you with healthy and glowing skin.

Apart from being an experienced dermatologist in Singapore, Dr Yong has earned multiple professional memberships relating to dermatology in various parts of the world. Should you notice your skin experiencing unwanted pigmentation, consult us to have your worries and blemishes zapped away with confidence!

Protecting from the sun has never been easier. Let us give you a hand on dealing with pesky ultraviolet lights. Contact us at AYD to book a consultation today.

References

Paul, S. P. (2019). Ensuring the safety of sunscreens, and their efficacy in preventing skin cancers: Challenges and controversies for clinicians, formulators, and regulators. Frontiers in Medicine, 6. https://doi.org/10.3389/fmed.2019.00195

Murali K. Matta, P. D. (2019, June 4). Effect of sunscreen application on plasma concentration of active ingredients. JAMA. Retrieved January 11, 2022, from https://jamanetwork.com/journals/jama/fullarticle/2733085

Autier, P., Dore, J.-F., Negrier, S., Lienard, D., Panizzon, R., Lejeune, F. J., Guggisberg, D., & Eggermont, A. M. (1999). Sunscreen use and duration of sun exposure: A double-blind, randomized trial. JNCI Journal of the National Cancer Institute, 91(15), 1304–1309. https://doi.org/10.1093/jnci/91.15.1304

Sander, M., Sander, M., Burbidge, T., & Beecker, J. (2020). The efficacy and safety of sunscreen use for the prevention of skin cancer. CMAJ: Canadian Medical Association journal 192(50), E1802–E1808. https://doi.org/10.1503/cmaj.201085

Latha, M. S., Martis, J., Shobha, V., Sham Shinde, R., Bangera, S., Krishnankutty, B., Bellary, S., Varughese, S., Rao, P., & Naveen Kumar, B. R. (2013). Sunscreening agents: a review. The Journal of clinical and aesthetic dermatology, 6(1), 16–26.

Song, H., Beckles, A., Salian, P., & Porter, M. L. (2020). Sunscreen recommendations for patients with skin of color in the popular press and in the dermatology clinic. International journal of women’s dermatology, 7(2), 165–170. https://doi.org/10.1016/j.ijwd.2020.10.008

Wang, P. W., Hung, Y. C., Lin, T. Y., Fang, J. Y., Yang, P. M., Chen, M. H., & Pan, T. L. (2019). Comparison of the Biological Impact of UVA and UVB upon the Skin with Functional Proteomics and Immunohistochemistry. Antioxidants (Basel, Switzerland), 8(12), 569. https://doi.org/10.3390/antiox8120569

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The Analysis of Sunscreen: How It Works And The SPF System