1 Find out the sunscreen index
To know the ability of sunscreen to protect against UV rays, people rely on SPF and PA numbers.
SPF (short for Sun Protection Factor) is a measure of the ability to resist UVB rays used in sunscreens, with the lowest being 15 and the highest being 100. According to international norms, 1 SPF is capable of Protect and limit the harmful effects of UV rays on the skin in about 10 minutes .
For example: Sunscreen with SPF 15 will protect the stomach within 150 minutes, SPF 50 will be about 500 minutes.
In addition, the SPF number also shows the percentage of ability to block harmful effects from UV rays. When placed in perfect conditions, a sunscreen with an SPF of 15 will block about 93.4% of UV damage, SPF 30 about 96.7%, and SPF 50 about 98%. However, this ratio is also relative in a certain period of time.
PA (short for Protection Grade of UVA) is a measure of a sunscreen's ability to filter UVA rays , published by the Japan Cosmetics Association. Usually on the sunscreen package, the PA index is shown with the "+" sign , which is understood as follows:
- PA + has UVA protection at 40 – 50%.
- PA++ has better UVA protection, at the level of 60 – 70%, the time is about 4-6 hours.
- PA+++ has good UVA protection, up to 90%, the time is about 8 – 12 hours.
- PA++++ has very good UVA protection, over 95%, over 16 hours.
However, you may not see the PA rating on some sunscreens today. Instead, there are abbreviations such as: UVA-UVB, UVA/UVB or UVA1, UVA2. Besides, there are separate symbols of manufacturers, countries, …
For example, SPF 60-12 means SPF 60 and PA+++.
2 Should I use a sunscreen with a high SPF/PA? How much SPF/PA is good?
Most people think that the higher the SPF/PA number, the better because the higher the ability to protect the skin against UV rays. However, this is not entirely accurate.
Using a sunscreen with a high SPF/PA, but not suitable for your skin , can cause allergic reactions and rashes. Besides, when using a type with a high SPF, it stays on the skin longer, easily causing clogged pores and damaging skin, quickly appearing signs of aging.
Normally, you should use SPF 30 – 60 sunscreen is just enough , but if you are someone with especially sensitive, inflamed or swollen skin, an SPF 15 – 30 sunscreen will avoid skin irritation, although However, the effectiveness of sunscreen is not high. With a very high SPF index of 60-100, you should only use it in areas of the skin that need to be protected from the sun, areas that are being treated for melasma or are allergic to sunlight.
For PA index, you should prioritize sunscreens with PA+++ or PA++ to provide better protection and longer protection time.
3 Myths about SPF/PA
Using a high SPF/PA sunscreen does not need to be reapplied
The higher the SPF/PA sunscreen, the more effective it is against UV rays, but it's only relative and depends on the time of using the cream. Therefore, on average, after 2-3 hours , you need to reapply sunscreen to best protect your skin.
Small dosage still ensures quality
Typically, you only use 1/2 to 1/4 of the required amount of sunscreen. For effective sun protection, you need to apply the FDA -recommended amount of 2 mg/cm2 of skin surface .
SPF is only needed when it's sunny
Even on cloudy days, UV rays can still damage your skin. Therefore, you should use sunscreen every day , not just for sunny days, with an SPF of 30 or higher.
If you have used sunscreen, you are not afraid of the sun
Sunscreen only helps limit the harmful effects of UV rays and is only relative. Therefore, you need to minimize your skin's direct exposure to the sun and wear more jackets , sundresses, masks, etc. to better protect yourself.
Above is the sharing of SPF and PA numbers on sunscreen. Don't forget to leave a comment if you have any questions that need to be answered!