Sunscreen 101: Everything you need to know about SPF

Sunscreen is the best commitment you can make to reduce premature skin ageing. We all know we need to wear it, but confusing SPF numbers, conflicting advice, and the vast array of product choices can make choosing the right sunscreen feel overwhelming.

Beyond just preventing sunburn, proper sunscreen use is crucial for shielding the skin from harmful ultraviolet rays that contribute to skin cancer and the visible signs of ageing. This blog post will demystify SPF and help you understand why it’s a critical tool in your daily skincare arsenal. We’ll explore the different types of rays, the meaning behind SPF numbers, and the importance of choosing a formula that works best for your skin type. Whether you’re a sunscreen novice or looking to refine your knowledge, we’ve got you covered with everything you need to know to protect your skin effectively.

What does SPF mean?

SPF stands for Sun Protection Factor, a numerical rating that indicates the level of protection a sunscreen provides against UVB rays—the type of solar radiation that leads to sunburn and can contribute to skin cancer. Essentially, the SPF number tells you how long the sun’s UV radiation would take to redden your skin when using the product exactly as directed, versus the amount of time without any sunscreen. For example, an SPF of 30 means theoretically, it would take you 30 times longer to burn than if you weren’t wearing sunscreen.


However, this factor isn’t a simple multiplier that guarantees extended time in the sun. The effectiveness of SPF also depends on factors like the intensity of the sun, the amount of sunscreen applied, whether you are sweating or swimming, and even your skin type.

Importantly, SPF primarily measures protection against UVB rays, and does not indicate how well the sunscreen will protect from UVA rays, which penetrate deeper into the skin and cause issues like premature ageing, wrinkling, and even skin cancer.

Unlike UVB rays, UVA rays are present during all daylight hours throughout the year and can penetrate clouds and glass, meaning you are exposed to them virtually every day, regardless of weather or if you are indoors. 

What Does the PA Rating Mean?

The PA rating system was developed in Japan and is used to indicate the level of UVA protection a sunscreen offers. The PA system ranges from PA+ to PA++++. More plus signs mean more protection, making this rating a helpful guide when looking for a product that offers significant defence against UVA rays.

What does Broad Spectrum Mean?

This is why the term “broad-spectrum” becomes important—it indicates that the sunscreen also provides protection against UVB and UVA rays.

Choosing a high-protection SPF and using it correctly is crucial to maximise your protection against all potential sun damage.

For facial sunscreen, dermatologists recommend choosing products with both a high SPF and PA rating – between SPF 30 and 50, and PA+++ or PA++++.

UVA, UVB, and Blue Light: How They Impact Your Skin

UVA (ultraviolet A) and UVB (ultraviolet B) rays, along with blue light, are the primary types of light that can have detrimental effects on the skin. UVB rays are the main cause of sunburn and play a significant role in developing skin cancer. They have a shorter wavelength, which means they are more potent at damaging the superficial layers of the skin. On the other hand, UVA rays have a longer wavelength that allows them to penetrate deeper into the skin, leading to premature ageing such as wrinkles and sunspots.

Blue light—part of the visible light spectrum emitted by the sun, and digital devices like smartphones and computers – penetrate even deeper than UVA rays. It’s associated with oxidative stress within the skin, which in turn leads to premature ageing and uneven skin tone. 

Chemical vs. Physical Sunscreen

Physical sunscreens use mineral ingredients like titanium dioxide or zinc oxide to physically block or reflect sunlight away from the skin.

Chemical sunscreens contain organic (carbon-based) compounds that work by absorbing UV light and converting it into heat, which is then harmlessly dissipated from the skin. These formulations are highly effective and often preferred for their lightweight feel and transparent finish, making them ideal for daily wear under makeup. Perfect for those who need durable, invisible sun protection, chemical sunscreens offer a practical solution for active lifestyles and prolonged outdoor activities.

Choose a sunscreen you love

Many people find sunscreen problematic. Common complaints include the greasy feel of some products, the white cast left by others, clogged pores, and difficulty finding a formula that sits well under makeup. The development of new formulations, however, has led to sunscreens that are lightweight and non-comedogenic, offer satin or matte finishes, and are suited for various skin types and tones without compromising protection.

At the end of the day, the right sunscreen for you is one you love to wear.

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