Stop checking sunscreen knowledge, the most comprehensive sunscreen guide is here!

Everyone has heard a saying: Ultraviolet rays are the most important cause of skin aging! Therefore, sunscreen is definite and necessary for everyone who loves beauty. Here I will teach you some necessary sunscreen knowledge.

1、 To protect erythema from ultraviolet rays (UVB, sun redness), mainly depends on the SPF value.

If the SPF of a sunscreen is 15, it means that assuming that a person will normally get red in 15 minutes without applying sunscreen, then after applying sunscreen with SPF 15, it can be guaranteed that she will sunburn her skin after 15 X 15 minutes, and so on.

If it is a long-term outdoor activity, you should choose sunscreen with SPF 30 or so. It is worth mentioning that the higher the SPF value, the greater the irritation to the skin and the easier it is to block pores. If you are often indoors, just choose one with SPF 15 or so.

2、 Protect long-wave dark spots from ultraviolet rays (UVA, tanning), mainly depending on the PA value.

PA is divided into three levels. PA + means that it can delay the tanning time of skin by 2-4 times, PA + + can delay it by 4-8 times, and PA + + + means that it can delay it by more than 8 times. In other words, girls who are afraid of tanning can choose sunscreen with higher PA + index.

Generally, it takes about 20 minutes for sunscreen to work, so just apply sunscreen 20 minutes before going out, and you can apply it again before going out. If you are going to the seaside, you need to choose sunscreen with higher SPF and PA index. The radiation at sea is very strong.

3、 About sunscreen clothing

Many cheap multicolored clothes on the Internet are actually useless. The Evaluation of UV Protection Performance of Textiles promulgated by the National Administration of Quality Supervision and Inspection shows that only when the UV protection coefficient (UPF) of the sample is greater than 30 and the UVA transmittance is less than 5%, it can be called a qualified "UV protection product". The test shows that many colorful sunscreen clothes on the Internet are far from reaching this index. Light colors will also reflect harmful light to unprotected faces, so it is better to wear a dark clothes.

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4、 Try to eat foods with sunscreen and avoid photosensitive foods.

Foods that help protect against the sun include vegetables and fruits rich in vitamin C, such as guava, kiwi, strawberry, cherry tomatoes, etc.; There are also soy products, nuts, cereals and tea that help protect against the sun.

Photosensitive food, on the other hand, is not suitable for outdoor activities. Photosensitive food refers to food that is easy to cause solar dermatitis. After digestion and absorption, photosensitive food will enter the skin. If it is exposed to sunlight, it will react with sunlight, resulting in skin redness, rash, and obvious itching, burning or tingling.

Common photosensitive foods in our life include lettuce, mustard, celery, spinach, coriander, lemon, mango, pineapple and so on.

5、 After-sun repair methods

Sometimes, despite complete sunscreen preparation, sunburn can't be avoided, so after-sun repair can relieve sunburn. Therefore, there are the following after-sun repair methods for your reference:

（1） Use cold compresses for red and hot hair.If the skin on your face and body is red and hot from sunburn, pour ice water on a cotton pad and apply it to your face. On your body, soak a towel with ice water and apply it to the sunburned part of your body. In cold compress, you can use water mixed with milk and normal saline, green tea frozen after soaking in boiling water, or distilled water directly.

（2） Hydrating and hydrating-Apply a mask. After sunburn, the skin water evaporates a lot, and it is extremely dehydrated, so it also needs a lot of water. Besides drinking a lot of water, it is also necessary to apply a hydrating mask. At this time, it is not suitable for whitening and other functional applications. You need to wait a few days for your skin to relieve before using whitening products to fade the pigment.