How should you use sunscreen with SPF?

Understanding the effects of the sun on the skin has impacted the progress in the technology of processing and producing sunscreens that are becoming more complex and complete. Accordingly, the choice of which sunscreen product is most suitable will depend on many factors such as how sensitive the skin is to cosmetics, dry or greasy skin, a previous history of skin cancer as well as the parameters on the product, it is important how much SPF in sunscreen is needed.

Before being able to delve into the details of the SPF of sunscreen, the first step is to understand the basics of sunscreen.

The sun is the source of two types of UV rays that are especially harmful to human skin: UVA and UVB rays. UVA rays penetrate deep into the skin, causing long-term lesions such as aging and wrinkles. On the other hand, UVB rays are shorter than UVA rays. They burn the surface of the skin, causing immediate damage such as sunburn and skin cancer in the long run.

Accordingly, sunscreen has been designed to protect the skin from harmful rays of the sun. The mechanism of action of sunscreens is shown in various ways, including absorption and deactivation, deterioration and reflection of rays.

Although in reality there are very few consumers who know what it is, the meaning of the SPF of sunscreen is actually quite simple. SPF stands for "Sun Protection Factor" and is a measure of sunscreen's ability to protect skin from UVB rays. The basic calculation of the ability to function in sunscreen is as follows: "If it takes 1 minute for unsused skin to start to redness in the sun, the use of sunscreen with SPF 15 will theoretically prevent skin reactions like this for 15 times longer."

Accordingly, suppose a person using sunscreen has an SPF of 30. If it usually takes 10 minutes until the skin begins to feel burning when out in the sun, using SPF 30 sunscreen, the skin will theoretically be protected from the sun for 300 minutes or 5 hours.

However, it is important to remember that the SPF only speaks to the protection of this product from UVB rays; these are rays that cause "redness of the skin" or burns to the surface. On the contrary, the SPF is completely without UVA rays; these are long-term harmful rays on the skin, including skin aging and wrinkle formation. Indeed, UVA rays can already cause a lot of harm to the skin before the skin begins to redness. In fact, one in five Americans has skin cancer in their 70s — and many of them are caused by UVA rays.

As a general rule, sunscreens with an SPF of less than 15 are considered to have a slight level of protection, SPF 15-30 is considered to have a moderate level of protection and higher than 30 SPF is considered to have a high level of protection.

Of these three levels, it's safe for the average user to use SPF 30 sunscreen, as long as it's applied in sufficient amounts and reapply regularly — but that's not the general rule for all. Determining the right sunscreen for yourself depends on the skin. Since sunscreens with SPF 15 are capable of filtering out about 93% of all UVB rays that reach the skin, SPF 30 filters to 97% and SPF 50 is 98%, these differences seem indetermible. However, for people who are sensitive to light or have a history of skin cancer, those additional percentages will make a significant difference.

A common assumption about the SPF is that the higher it is, the more likely it is to protect the skin from the sun. If used correctly as directed in a controlled environment, such as a laboratory with a good climate, a stable amount of UVB exposure and the in addition to other external factors affecting its performance, this assumption is absolutely true. However, it is highly unlikely that people will always remain in such an "ideal" environment. Moreover, other factors such as sweating and exposure to water such as swimming, bathing will reduce the effectiveness of the SPF. This is the explanation why most experts warn that in fact, no sunscreen can last longer than 2 hours.

As already mentioned, the SPF actually refers only to protection against UVB rays — but it's not the only one that can harm the skin. Meanwhile, UVA rays also cause long-term damage to the skin such as skin aging and wrinkle formation, and can also do a lot of harm before the skin begins to feel burned. The fact of sunscreen is that it is not enough to protect only from UVB rays, this is the context of the wide spectrum sunscreen that was born.

Sunscreens are called "broad spectrum" when resistant to both UVA and UVB rays. And, to be honest, this is an obvious imperative. In order for sunscreen to be considered "broad spectrum", the UVA resistance of this product must be commensurate with UVB resistance. As the SPF, which protects UVB rays, increases, UVA resistance must also increase proportionally. Therefore, this is also an important factor to note when choosing to buy sunscreen, instead of merely considering based on the SPF.

The first thing to remember when applying sunscreen is that most people tend to apply not enough. Experts estimate most people only use between 25% and 50% of the recommended amount of sunscreen per use.

Moreover, there are some areas of the skin that are often exposed to strong sun exposure but are easily missed such as the neck, ears, nose, lips and feet. In addition, if using a spray sunscreen, re-use may not make it simpler. In fact, the use of spray sunscreen is much more difficult to control, since the amount of cream is mainly covered in a very thin layer like a film on the face of the skin instead of seeping into the skin; at the same time, improper spraying of sunscreen or ingredients that act as a pusher in the aerosol can also make the skin more susceptible to hypersensitivity.

The next thing is that applying sunscreen if only done once is not enough. Dermatologists are always encouraged to reapply sunscreen every 90 minutes if it is still outdoors. Besides, if you are doing a lot of physical activity, sweating, swimming or drying people with a towel, users must also reapply sunscreen immediately.

On the other hand, keep in mind that sunscreen is not only mandatory to be used on sunny days. Whether the weather is sunny or cloudy, sunscreen is always an important part of each person's daily skincare routine.

Finally, although quality sunscreens and suitable clothing can protect the skin from the harmful effects of the sun, people should also avoid working outside during the daytime peak hours. Look for shade between 10am and 4pm – when the sun has peaked and is more likely to suffer skin damage, especially in people with irritated skin muscles. Even in winter, it is cloudy, less sunny, sun protection is still very important. And users should also protect themselves indoors and when driving because the sun can penetrate the window. In the car, transparent insulation films can block out the sun's rays; at home, it is recommended to pull the curtains during peak sunny hours to limit the amount of UV rays that can enter the house.

In summary, the brands on sunscreen products contain key information that helps users evaluate their effectiveness. In particular, the SPF sunscreen index, a figure that reflects the skin protection of sunscreen from sunburn rays is often of top concern. In addition, the choice of sunscreen is based on other criteria such as broad spectrum protection against premature skin aging rays and water resistance for a certain period of time to help protect the skin most comprehensively.

Source: colorescience.com, healthline.com