Sunscreen products are a must-have "weapon" for women who love beauty, but the sun protection factor "SPF" is not as high as possible. The Ministry of Health recently reiterated the regulations on sunscreen cosmetics labeling. The sun protection index can only be labeled "SPF30+", but there are still some sunscreen products on the market that are marked as SPF30 or above.

According to the relevant regulations of the Ministry of Health, when the sun protection factor of the tested product, that is, the SPF value is greater than 30, and is still greater than 30 after subtracting the standard deviation, the maximum can only be identified as "SPF30+", and the measured value cannot be identified. The staff of the quality supervision department of Taiyuan City reminded consumers that the higher the sun protection index, the heavier the skin burden. Some sunscreen products also have problems such as excessively high SPF value, sunscreen index shrinkage, concept hype, etc. "The selection of sunscreen products should be determined according to their skin condition, occupation and specific use environment. Do not blindly choose products with high SPF value. Any sunscreen will cause a burden on the skin. The higher the sunscreen index, the more greasy the skin will be. The high-index sunscreen will have a certain stimulating effect on the skin while fighting UV rays. It should be used with caution."

What is SPF?

SPF is the abbreviation of SUN Proteetion Factor, which indicates the level of sun protection that sunscreen products can exert. It is based on the lowest erythema dose of the skin.

The skin becomes red after sun exposure, medically known as "erythema", which is the slightest reaction of the skin to the sun. The minimum erythema dose is the shortest sun exposure time for erythema on the skin. After using sunscreen, minimum erythema dose skin will grow, then the sunscreen with a sun protection factor of SPF product was: SPF = minimum erythema dose (with sunscreen after) / minimum erythema dose (with sunscreen before)

Assuming that the minimum erythema dose of a person's skin is 15 minutes, then after using a sunscreen with an SPF of 4, theoretically it can stay in the sun for 4 times (60 minutes), the skin will appear reddish; if SPF is 8 Sunscreen can stay 8 times in the sun (ie 120 minutes), and so on.

SPF is currently widely used in the world to characterize the sunscreen efficacy of sunscreen products. Foreign countries generally use human skin tests or other methods to determine. At present, China has not established a standard for measuring SPF values. This test uses another method of international evaluation of sunscreen efficacy of sunscreen products - spectroscopy. It evaluates the sunscreen efficacy of sunscreens by measuring the absorbance value (OD) that characterizes the ability of the sample to absorb and reflect ultraviolet light.