In this comprehensive guide, we delve into the intricacies of sunscreens, exploring their types, ingredients, application techniques, and the critical role they play in sun protection. We try to clarify confusing terms and aim to make sunscreen knowledge accessible to the general public.
Ultraviolet Light (UV)
The sun transmits three wavelengths of UV radiation: UVA, UVB, and UVC.
· UVA rays go deeply into the skin and play a major part in skin aging and wrinkling. They also contribute to the growth of skin cancer.
· UVB rays are the main culprit for sunburns. They damage the skin’s outer layers and play a key role in the development of skin cancer.
· UVC rays do not reach our skin as they are absorbed by the Earth’s atmosphere.
Choosing the Right Sunscreen
When selecting a sunscreen, aim for adequate protection against both UVA and UVB rays. Sunscreen that give protection against both types of UV are called broad-spectrum and offer comprehensive coverage against sunburn, premature aging, and skin cancer.
The amount of protection against UVB is designated by the SPF rating of a sunscreen, whereas the amount of protection against UVA is indicated in more than one ways (such as the PA+ system, the star system, or the UVA circle logo).
Sun Protection Factor (SPF)
SPF measures a sunscreen's ability to prevent UVB rays from penetrating the skin and causing sunburn. The higher the SPF number, the greater the protection it offers. SPF only relates to UVB protection and not UVA.
SPF indicates the time it would take for UVB rays to redden the skin when using a sunscreen, compared to the time it would take without any protection. For example, if your skin typically burns within 10 minutes of sun exposure without protection, an SPF 30 sunscreen theoretically extends that time to 300 minutes.
However, SPF doesn't provide a linear increase in protection. SPF15 blocks about 93% of UVB rays, whereas SPF30 filters out about 97% of UVB, and SPF 50 filters out around 98%.
A minimum of SPF 30 is recommended. Even though the difference in protection between SPF 30 and SPF 50 is relatively small, it is important to note that higher factors will allow you significantly more sun exposure time before your skin is damaged by sun burn and cancer causing UVB rays.
UVA protection ratings
UVA protection ratings are more complicated than SPF and can be indicated in a number of ways.
UVA circle logo
The European Commission (EC) recommends that the UVA protection offered in a sunscreen should be at least one third of the related SPF. Sunscreens meeting this requirement are eligible to display a UVA logo, with the letters UVA enclosed within a circle. If this circle is on a product, then you can rest assured that it meets EC Guideline recommendation standards for UVA protection.
PA+ system
Some sunscreens, most notably those in Asia, include PA+ ratings on their products. The PA system (Protection Grade of UVA) uses plus signs to denote increasing levels of UVA protection, with more plus signs indicating higher protection.
This is what each PA+ rating means:
· PA+ some UVA protection
· PA++ moderate UVA protection
· PA+++ high UVA protection
· PA++++ extremely high UVA protection
Star system
The star system has been introduced by the retailer Boots and is mainly used in the UK.
Star ratings range from one to five stars. The more stars a sunscreen has, the better it is at filtering out UVA rays.
Confusingly, a high star rating does not actually indicate a high level of UVA protection. Instead, it relates to the product’s ratio of % UVA absorbed compared to UVB.
Therefore, if a product has a low SPF, it can still have a 5 star rating – not because it offers high UVA protection but because the ratio of UVA to UVB is good. In this case the UVB protection would be too low and so would the UVA protection be.
STAR RATING | UVA/UVB RATIO |
3 stars | 0,60 – 0,79 |
4 stars | 0,80 – 0,89 |
5 stars | 0,9 or more |
Sunscreen types and ingredients
Sunscreens come in two primary forms: chemical and physical (mineral) sunscreens.
Chemical sunscreens work by absorbing UV radiation and converting it into heat, while physical sunscreens create a barrier on the skin's surface, deflecting and scattering UV rays.
Chemical sunscreens typically contain active ingredients such as avobenzone, oxybenzone, and octocrylene, among others. These ingredients offer broad-spectrum protection against both UVA and UVB rays.
Physical sunscreens rely on minerals such as zinc oxide and titanium dioxide to provide UV protection. These minerals sit on the skin's surface, forming a physical barrier that reflects and scatters UV radiation away from the skin.
Sunscreen Application
Proper application of sunscreen is essential for effective sun protection. Sunscreen should be applied generously to all exposed skin areas at least 15 minutes before sun exposure, and then re-applied every two hours.
More frequent applications are necessary if swimming, sweating, or towel drying, as these can reduce its effectiveness.
Even though formulated to resist being washed off, even the efficacy of water-resistant sunscreens will reduce after swimming. Moreover, towel-drying can easily remove up to 85% of a sunscreen’s effectiveness.
Unfortunately, no sunscreen can offer adequate all-day protection, even if advertised as such.
How long to use for
Once opened, the longevity of a sunscreen can vary depending on several factors, including the formulation, storage conditions, and expiration date.
Once past the expiration date, the sunscreen starts losing its efficacy, making it less reliable for sun protection.
Proper storage can help extend the shelf life of sunscreen. Store sunscreens in a cool, dry place away from direct sunlight and high temperatures, as exposure to heat and light can degrade the product over time. Avoid leaving sunscreens in places with extreme temperatures, such as hot cars.
Pay attention to any changes in the appearance or consistency of the sunscreen. If the product changes colour, texture, or develops an unusual odour, it may be a sign that it has degraded and should be discarded.
As a general rule of thumb, and to ensure maximum effectiveness, it is advisable to replace sunscreens yearly even if they are not past their expiry date.
Additional tips
In addition to using sunscreen, it is important to also practice other sun safety measures, such as wearing protective clothing (wide-brimmed hats, sunglasses, and lightweight, long-sleeved clothes), and seeking shade during peak sunlight hours (typically between 10 a.m. and 4 p.m., when UV radiation is most intense).
Reflection of the sun’s rays can greatly increase the power of UV radiation, and should be taken into consideration. For example, the presence of snow can increase UV radiation by up to 85%, whereas sand can increase it by up to 17%, and water by up to 5%.
Reef-safe (or ocean-friendly) refers to sunscreens that are formulated without certain chemicals that are thought to harm coral reefs and marine ecosystems. Traditional sunscreens often contain ingredients such as oxybenzone, octinoxate, octocrylene, and homosalate that contribute to coral bleaching, disrupt coral reproduction, and harm marine life. Reef-safe sunscreens use alternative ingredients that are considered less harmful to coral reefs and marine ecosystems.
It is also advisable to incorporate sunscreens into your daily skincare routine, and embrace sun protection as an essential component of maintaining healthy, radiant skin for years to come.
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