If you don't understand what SPF20PA++ means, how dare you call yourself a delicate pig girl?

Many girls who are new to skin care say that they don’t understand the SPF of sunscreen. Today we will take a look at what SPF20PA++ means and understand how the SPF of sunscreen is determined. If you take good care of your skin every day, you must collect this!

What does SPF20PA++ mean?

The sun protection index SPF20PA++ needs to be split into "SPF20" and "PA++". The first SPF20 means that the sunscreen product can absorb 95% of UVB medium-wave ultraviolet rays under laboratory conditions (the algorithm is: (20-1)/20*100% = 95%).

The "PA++" in the SPF20PA++ sun protection index indicates that it delays tanning time by 4-8 times and refers to the ability to protect against long-wave UVA ultraviolet rays.

What do different levels of SPF and PA mean?

SPF 30 = (30-1)/30*100% ≈ 96.67%, which means that about 3.33% of UVB rays can reach the skin;

SPF 50 = (50-1) / 50 * 100% = 98%, which means that only 2% of UVB can reach the skin.

PA+: Delays tanning time by 2 to 4 times.

PA++: Delays tanning time by 4 to 8 times.

PA + + +: Delays tanning time by more than 8 times.

When to use SPF20PA++ sunscreen

SPF20PA++ is more suitable for short-term outdoor or indoor sun protection on cloudy days. If you plan to be outdoors for a long time, it is not recommended to use SPF20PA++ sunscreen. Because SPF20PA++ sunscreen is best reapplied every 30-40 minutes when the user is outdoors, it is more troublesome.

If girls engage in outdoor activities for a long time, they should use products with SPF30 or above and a PA value of at least three +. In addition, they need to wear sunscreen to protect their skin.

What UV rays does SPF20 protect against?

SPF20 means that the product's ability to protect against medium-wave ultraviolet rays (UVB) reaches 95%. The penetrating power of medium-wave ultraviolet rays is not as strong as that of UVA. Most UVB is blocked by the atmosphere, but a small amount is absorbed by the skin epidermis. UVB can cause sunburn, redness, and even blisters on the skin in a short period of time. Long-term exposure to the skin can cause erythema, inflammation, skin aging, and in severe cases, skin cancer.

Fortunately, we have a more intuitive sense of UVB. Generally speaking, if we feel that the sun is very strong, it means that the UVB is relatively strong. On rainy days, the UVB will be relatively weak.