November 24, 2023 Longchang Chemical

What does SPF stand for in sunscreen products and does a higher SPF mean better results?

1. UVB and UVA do different damage to the skin

UVB has a shorter wavelength (290-320 nm) and stronger energy, which can make our skin red and sunburned in a short time. However, UVB penetration is weaker, so most of the UVB in sunlight is blocked by the ozone layer, and only a small portion reaches the earth’s surface, and we generally only get red and sunburned skin when the sun’s rays are particularly strong. UVB may lead to skin cancer if exposed for a long time.
In contrast, UVA has a longer wavelength (320-400 nm) and lower energy, but it is so penetrating that it can reach the earth’s surface all year round, regardless of whether it is sunny or cloudy, and even irradiate into the dermal layer of our skin. In the short term, UVA can cause skin sensitivity and decreased tolerance, and in the long term, it can cause melanin deposition and accelerate skin aging, which means that UVA can make our skin darker and wrinkled. In addition, UVA can also induce skin cancer.

Therefore, when we choose sunscreen, both UVA and UVB protection are important. On cloudy days, people tend to neglect using sunscreen, but UVA can shine into the dermal layer of the skin just as well. We need sunscreen all year round, the most easily ignored, and the optimal necessity to protect all year round is UVA.

Currently, many sunscreens are better at protecting against UVB than UVA.

2. The significance of SPF and PA values

SPF: The ability of a sunscreen product to protect against UVB rays that can burn the skin. For example, a bottle of sunscreen with an SPF of 20 means that it will increase your skin’s tolerance to UVB rays by 20 times when applied. Assuming that your skin will be reddened by 10 minutes of sun exposure without sunscreen, it will take roughly 15*20=200 minutes of sun exposure after applying a sunscreen with an SPF of 20 to be reddened.

Many people mistakenly think that SPF refers to the time related to continuous sun protection, for example, SPF50 can provide protection for more than three times the time of SPF15 sunscreen. Such an understanding is wrong. In fact, SPF is not directly related to the amount of time spent in the sun, but rather to the amount of light exposure. At midday, when the sun is strong, you’ll be more likely to get sunburned than in the morning and evening, and at lower latitudes (such as Guangzhou vs. Xinjiang), where the sun’s intensity is also higher, you may need to reapply sunscreen more often.

PA (protection grade of UVA) is the ability to combat UVA, followed by the more + sign, indicating the stronger the ability to prevent sun tanning. But not all products have PA mark, many European and American sunscreen can not be seen on the PA, but does not mean that they may not want to tan, but just use other labeling methods, such as PPD persistent hyperpigmentation coefficient.

Differences Between Sunscreen SPF Ratings (e.g., SPF20, SPF30, SPF50):


Provides moderate protection against UVB rays.
Blocks about 95% of UVB rays.
Suitable for everyday activities with limited sun exposure.

Offers higher protection than SPF20.
Blocks about 97% of UVB rays.
Recommended for extended outdoor activities.

Provides the highest level of UVB protection.
Blocks about 98% of UVB rays.
Recommended for individuals with fair or sensitive skin, prolonged sun exposure, or those at higher risk of skin cancer.
Key Points:

Incremental Protection: The difference in protection between SPF ratings is not linear. For example, SPF 30 does not offer double the protection of SPF 15. SPF 30 provides about 4% more protection than SPF 15, and SPF 50 provides only about 1-2% more protection than SPF 30.

UVB Protection: SPF primarily measures protection against UVB rays, which are responsible for sunburn. It does not provide a complete measure of protection against UVA rays, which contribute to premature aging and skin cancer.

Reapplication: Regardless of the SPF level, it’s crucial to reapply sunscreen every two hours or more frequently if swimming or sweating. No sunscreen provides 100% protection, and reapplication is essential for continued effectiveness.

Skin Type: The choice of SPF can depend on an individual’s skin type, sun sensitivity, and the duration of sun exposure. Those with fair or sensitive skin may opt for higher SPF levels.

Consider Other Sun Protection Measures: Sunscreen should be part of a comprehensive sun protection plan, including seeking shade, wearing protective clothing, and avoiding peak sun hours.

The Higher the SPF, the Better?

While it might seem logical that higher SPF offers better protection, the incremental increase in protection diminishes as SPF levels rise. SPF 30 is generally considered to be sufficient for most people, offering significant protection against UVB rays. SPF 50 provides a slightly higher level of protection and may be recommended for specific situations, such as extended outdoor activities or for individuals with higher sun sensitivity.

It’s essential to note that no sunscreen provides complete protection, and other sun protection measures should be employed, especially in intense sunlight. Additionally, UVA protection, which is not indicated by SPF, is crucial for overall sun protection. Look for broad-spectrum sunscreens that protect against both UVA and UVB rays.

Ultimately, choosing the right SPF depends on individual factors such as skin type, planned sun exposure duration, and personal preferences. It’s advisable to consult with a dermatologist for personalized recommendations based on specific skin needs and concerns.

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