How often should you apply sunscreen? The time varies depending on the situation.

How often should you reapply sunscreen? I believe that girls know more or less that sunscreen needs to be reapplied, right? So how often should sunscreen be reapplied is the best time? Do you know? If you don’t know, let’s take a look below~

Reapply sunscreen every few hours

The time to reapply sunscreen is not fixed, but it needs to be determined according to the SPF value of the sunscreen you buy and the environment you live in.

SPF value

The SPF value of sunscreen refers to the ability of sunscreen to block ultraviolet UVB, that is, its ability to prevent skin from sunburn. Generally speaking, the higher the SPF value of the sunscreen, the longer it can protect against ultraviolet UVB. Girls can use the following formula to calculate that if human skin is directly exposed to the sun without any protective measures, the time for erythema to appear is about 20 minutes. If SPF15 sunscreen is used, the protection time can be increased to 20 times 15 = 300 minutes. If you use SPF 30 sunscreen, the protection time against UVB rays can be extended to 20 times 30 = 600 minutes. Then girls can use this analogy to determine how often it is best to reapply their sunscreen.

environment

The time to reapply sunscreen should be determined according to the environment you are in. If you are indoors and sweat less, then the time can be a little longer, and it is okay to reapply every 3-4 or 4-5 hours. However, if you are outdoors, exposed to the sun and sweating a lot, the reapplication time should be shortened, and it is best to reapply every 1-2 hours.