Sun Protection Factor (SPF): what it means and how to protect your skin from the sun

Name: Bernard Cassière Diamond Pack
Brand: Bernard Cassière
Price: 179.00 EUR
Availability: InStock

August 13, 2026

What are UVA and UVB rays?

Ultraviolet (UV) radiation is not visible, but it can affect our skin even when we don't feel intense heat.

The main types of UV radiation that reach the Earth's surface are UVA and UVB, and both can cause skin damage.

UVB rays

UVB rays are the main cause of sunburn and play a significant role in the development of skin cancer.

UVA rays

UVA rays penetrate deeper into the skin and are closely linked to photoaging, the appearance of wrinkles, and other visible signs of skin aging.

That is why, when choosing a sunscreen, you should not only look at the SPF number: look for a product that offers broad-spectrum protection against UVA and UVB.

What does SPF mean?

SPF stands for Sun Protection Factor.

It is the number that appears on sunscreens such as SPF 30, SPF 50, or SPF 50+.

SPF is primarily used to indicate the level of protection against UVB radiation, which is linked to sunburn. For this reason, a product with a high SPF does not replace the need to seek shade, wear protective clothing, or limit sun exposure.

Does SPF 50 provide double the protection of SPF 25?

Not exactly. The SPF number should not be interpreted as a multiplier of the time you can stay in the sun.

Actual protection depends on many factors: amount applied, reapplication, sweat, water, friction, UV radiation intensity, and individual skin characteristics.

Never use SPF to calculate how long you can sunbathe.

Which SPF to choose: 30 or 50?

For prolonged outdoor exposure, a good general choice is a broad-spectrum sunscreen with SPF 30 or higher. For situations of intense sun exposure, vacations, beach, mountains, or particularly sensitive skin, many people opt for SPF 50 or SPF 50+.

The most important thing is not just to choose a high number, but to apply enough product and reapply it correctly.

What does UV radiation intensity depend on?

The amount of ultraviolet radiation our skin receives can vary considerably.

☀️ Time of day: UV radiation is usually most intense around noon.
🌍 Geographic location: Intensity can be higher near the equator.
☁️ Cloud cover: Clouds do not eliminate UV radiation.
⛰️ Altitude: UV radiation increases at higher altitudes.
🏖️ Reflective surfaces: Sand, water, and snow can reflect UV radiation.

How to apply sunscreen correctly?

Apply it before sun exposure — approximately 20–30 minutes before going out.
Use a sufficient amount — for an adult's body, approximately 30 ml.
Do not forget small areas — face, neck, ears, nose, décolletage, shoulders, hands, tops of feet, and lips.
Reapply — every two hours and after swimming, sweating, or towel drying.

What is the UV index?

The ultraviolet index (UVI) indicates the intensity of ultraviolet radiation at a given place and time. The WHO recommends taking sun protection measures when the UV index is 3 or higher.

Sunscreen is not the only protection

🧴 Sunscreen — broad-spectrum, SPF 30 or higher.
👒 Hat — wide-brimmed for face, ears, and neck.
👕 Clothing — physical barrier against UV radiation.
🕶️ Sunglasses — protection against UVA and UVB.
🌳 Shade — especially during hours of peak intensity.
⏰ Limit exposure — avoid the sun when radiation is most intense.

Sun protection and photoaging

Cumulative exposure to UV radiation contributes to photoaging. Incorporating a broad-spectrum sunscreen into your daily routine is one of the most important decisions for long-term skin care.

Which sunscreen to choose?

You can find different formats: sun cream, facial fluid, spray, sun stick, and water-resistant sunscreen. The important thing is to choose a product suitable for your skin and the type of exposure.