How much SPF/PA sunscreen is good?

This is an automatically translated article.

SPF and PA are two indicators that indicate a sunscreen's ability to protect against UV rays. When choosing a sunscreen should pay attention to these two indicators.

1. SPF and PA

1.1. SPF (sun protection factor) according to the FDA is a measure of the protection against UVB rays used in sunscreens. This index is calculated according to the number of hours and percentage of UV protection when using sunscreen on the skin.
SPF in sunscreens is as low as 15 and as high as 100, 1 SPF has the ability to protect skin and limit the harmful effects of UVB rays for about 10 minutes.
Meaning of SPF index on sunscreen: There are 2 common interpretations
Understanding by time of UV protection: That is, multiplying SPF by 10 to calculate the time to protect skin against harmful effects of UVB rays in minute. For example, a sunscreen with an SPF of 30 will protect the skin from UVB rays for 300 minutes. Percent UV protection: When placed in perfect conditions, a sunscreen with an SPF of 15 will block about 93.4% of damage from UVB rays, SPF 30 is about 96.7%, SPF 50 is about 98%. However, this ratio is also relative in a certain period of time.

1.2. PA index (protection grade of UVA) is an index that measures the ability to protect the body from UVA rays of sunscreen announced by the Japan Cosmetic Association. How to read and understand the meaning of PA index on sunscreen : Usually on the sunscreen package, the PA index is shown poorly according to the "+" sign, which is understood as follows:
PA + has the ability to block UVA rays at 40-50% PA++ ability to block UVA rays. better, at levels from 60-70% PA+++: Good UVA protection, up to 90% PA++++: Very good UVA protection, up to over 95%.

2. Should I use a sunscreen with a high SPF?

Most people assume that the higher the SPF, the better because of the higher the ability to protect the skin against UV rays. In reality, however, this is not entirely true.
Why should consider when using a sunscreen with a high SPF:
The use of a sunscreen with a high SPF is not necessarily suitable for the user's skin. Sunscreens with a high SPF often focus on protecting against UVB rays rather than UVA rays. The sun protection time of a sunscreen with an SPF above 60 is not much better than that of SPF 50, but when using a high SPF type, it stays on the skin longer, easily causing clogged pores and damaging the skin. damage, thereby rapidly appearing signs of skin aging.

3. How much SPF sunscreen is good?

According to dermatologists, we should use sunscreens with SPF from 30 to SPF 60.
Sunscreens with SPF less than 30, do not bring the expected effect. . However, if your skin condition is acne causing inflammation and swelling, you should only use a sunscreen with an SPF of 15-30 to avoid irritating the skin.
With very high SPF values ​​from 60-100, it should only be used in special areas of the skin that need to be protected from the sun such as skin that is being treated for melasma or is allergic to sunlight.
Choosing the best sunscreen for your skin depends on the SPF index. Not every higher SPF is better, because it can cause damage to the skin and the sun protection is no more effective than lower SPF types.

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