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How often should I reapply sunscreen

Overview​

Now that you've read the importance of sunscreen (Link), you've probably understood why you should apply it every time. However, if you apply it only once, the effect doesn't last long. Therefore, the cosmetics industry recommends applying it again every two to three hours.

But the criteria are also ambiguous. This is because each person has a different skin type and varies depending on the type of sunscreen. In this post, let's find out how often we have to reapply sunscreen.

Reapplying time, based on SPF and PA.

We often choose the sunscreen products we use based on SPF or PA. Please refer to the link for details if you are not well aware of SPF and PA. (Link)

It is said to have a shut-off duration of 15 minutes per SPF, so if I apply SPF50, will the effect be maintained for 12 hours? 
"Answer is NO"
This is only a figure that can be achieved under a well-set environment, and it is far from the actual environment we use sunscreen.

For example, our skin constantly breathes. It releases sweat, and sebum periodically. And we do not have control over how much sweat and sebums are secreted. This depends on what skin type the user has and how much sweat and sebums one emits.

There may also be differences depending on the environment in which we live. You can be in a humid or dry environment, sometimes raining or playing in the sea. It should be noted that SPF levels do not have a constant effect depending on this environment.

Reapplying time, based on inorganic and organic sunscreen

If you want to know more about inorganic and organic sunscreens, please refer to the link. (Link)

In fact, there is no significant difference between inorganic and organic sunscreen when it comes to the concept of reapplying. 

Some say that inorganic sunscreens are made of metal components such as titanium dioxide or zinc oxide, so there is common sense that it does not have to be reapplied over time.

But this is wrong. Sunscreen continues to disappear for several reasons, including when we touch our skin, when we use our cell phones, and when we change our clothes, as well as the secretion of sebum and sweat. In the end, it is essential to reapply the sunscreen whether it is an inorganic sunscreen or an organic sunscreen.

Conclusion

I think the importance of reapplying sunscreen has been fully explained. Then, how often should we reapply? 

In fact, there is no clear answer to this question. This is because the difference is very large depending on the situation and environment. However, there are some indicators for people who wear makeup. It's the time when the makeup is removed unintentionally. 

Makeups are either removed or erased due to sebum secretion and moisture of surroundings. And this can be observed with the naked eye.

Like other cosmetics, sunscreen is also applied on the skin. The disappearance or fading of color cosmetics means that sunscreen has also been removed. If so, it can be seen that the time when makeup is removed or faded is the time to reapply sunscreen.

Makeup is getting lighter or erased = Need to reapply sunscreen

In the case of oily skin, it may be necessary to apply it again within 2 to 3 hours in general and 1 to 2 hours in severe cases. Conversely, dry skin may be maintained for as long as 5 to 6 hours. Therefore, you can determine how often you should reapply while checking your skin condition and color makeup condition.

Source

Location: South Korea

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