Sunscreens: Sunscreens containing chemicals that filter out UVB rays and protect the skin should be used before direct exposure to strong sunlight. In the past, sunscreens often only filtered UVB, but many new sunscreens now also have broad-spectrum sun protection that effectively filters UVA. Sunscreens contain substances that absorb UVB, such as para-aminobenzoic acid (PABA) and benzophenone. Because PABA does not immediately adhere firmly to the skin, sunscreens containing PABA must be applied 30 minutes before going into the sun or water. PABA may irritate the skin and cause contact dermatitis in some people. Many sunscreens contain PABA and benzophenone or other substances, and these combined formulations block a wider range of wavelengths of UV rays. Many sunscreens claim to be water-resistant or water-resistant, but despite this, most of these products still need to be reapplied after swimming or sweating. There are also sunscreens called shades that contain substances with physical barrier functions such as zinc oxide or titanium dioxide. These thick, white ointments block almost all sunlight and can be used on sensitive areas such as the nose and lips. Some cosmetics contain zinc oxide or titanium dioxide. Newer sunscreens with thinner textures and more natural colors can be used in combination with other traditional chemical sunscreens for better sun protection. In the United States, the sun protection index (SPF) is used to evaluate the performance of sunscreens, and the higher the SPF value, the better the protection. Sunscreen index in 2-12 provides minimum protection, index in 13-29 provides medium protection, index in 30 and above can provide maximum protection. But SPF can only rate the performance of protection against UVB, while there is no rating standard for UVA.