防晒标签指南：轻松看懂SPF、PA，告别选择困难！

Sunscreen Label Guide: Decoding SPF, PA & Beyond

即使在紫外线相对温和的冬季，做好防晒依然是日常护肤重要的一步。面对产品上各种专业标识，如何精准解读？本文将帮助您化繁为简，快速掌握防晒标签的要点。

While UV radiation may be milder in winter, sun protection remains an essential step in daily skincare. With various technical terms on product labels, how can consumers make informed choices? This guide simplifies key sunscreen labeling information for everyday understanding.

「防晒伤关键：SPF值 / UVB Protection: Understanding SPF」

SPF（Sun Protection Factor）是通用的UVB防护指数。UVB是导致皮肤晒红、晒伤的元凶。

SPF (Sun Protection Factor) is the universal metric for UVB protection - the primary cause of sunburn and skin reddening.

1. 定义

SPF值基于“最小红斑量（MED）"——即导致皮肤刚刚开始出现肉眼可见发红（也就是晒红）所需的最小紫外线剂量。

根据ISO24444的人体测试法，SPF=涂防晒霜后的MED ÷ 未涂防晒霜的MED。

简单理解，SPF值代表延长皮肤被晒伤所需时间的倍数。

1. Definition

SPF is calculated based on Minimal Erythema Dose (MED) - the minimum UV exposure required to cause just-visible skin reddening. According to ISO24444 human testing protocols:

SPF = MED with sunscreen ÷ MED without sunscreen

Essentially, SPF indicates how much longer protected skin can withstand UV exposure before burning compared to unprotected skin.

2. 防护效率

SPF值越高，对UVB的阻挡率越高，但并非线性增长。

SPF30 ≈ 可阻挡97%的UVB

SPF50 ≈ 可阻挡98%的UVB

值得注意的是，SPF值从30提升到50，阻挡率仅提高了1.3%，但产品质地通常会变得更厚重。

2. Protection Efficiency

Higher SPF values block more UVB, but not proportionally:

• SPF30 ≈ 97% UVB blockage

• SPF50 ≈ 98% UVB blockage

Note: While SPF50 only provides 1.3% more protection than SPF30, the formulation typically becomes heavier.

3. 常见误区纠正

• 错误观念：SPF值能直接换算成固定的“安全保护时长"。

• 正确观念：防晒效果会因使用量、环境因素等动态变化，所以SPF值代表的是对紫外线剂量的阻挡能力，而非一个固定的时间承诺。如果涂抹量不足，即使使用SPF50的产品，实际防护效果也会大打折扣，可能降至SPF10左右。

3. Common Misconceptions

• Myth: SPF directly converts to guaranteed "safe sun exposure time"

• Fact: SPF indicates UV dose blockage capacity, not fixed time protection. Real-world factors like application amount and environmental conditions significantly impact effectiveness. Insufficient application (less than 2mg/cm²) can reduce SPF50 performance to SPF10 levels.

「防晒黑/防晒老关键：UVA防护 / UVA Protection: Preventing Tanning & Aging」

UVA是导致皮肤晒黑、老化和产生皱纹的主要因素。目前每个地区对UVA的防护标准尚未统一，主要有以下三种体系：

UVA causes skin darkening, aging and wrinkles. Global UVA protection standards vary:

1. 中日韩标准：PA指数

PA等级基于PFA值（防护UVA指数），看皮肤要多大的紫外线量才会开始被晒黑。用“+"号表示防护强度：

PA+：PFA 2-3，轻度防护效果

PA++：PFA 4-7，中度防护效果

PA+++：PFA 8-15，高度防护效果

PA++++：PFA≥16，超高度防护效果

“+"号越多，越不容易晒黑，防护UVA的能力越强。

1. Asian Standard: PA Rating

PA grades based on Protection Factor of UVA (PFA) - measuring UV dose required to induce tanning:

• PA+: PFA 2-3 (basic protection)

• PA++: PFA 4-7 (moderate protection)

• PA+++: PFA 8-15 (high protection)

• PA++++: PFA≥16 (very high protection)

More "+" symbols indicate stronger UVA protection. China's highest rating is PA++++.

2. 美国标准：广谱防晒（Broad Spectrum）

美国不采用PA值，而是采用“广谱防晒"标准。产品必须同时满足：

• SPF值≥15

•临界波长（CW）≥370纳米

达标的产品可标注“Broad Spectrum"。未达标的产品则需在标签上注明警示语，提示该产品仅能防晒伤，不能预防皮肤癌或皮肤老化。

注：临界波长（CW）：由美国皮肤科医学会提出。指防晒产品经过测试后能阻断90%紫外线的zui大波长，简单来说，CW数值越高，能够防护的波长范围越广，对紫外线的防护效果越好。

2. US Standard: Broad Spectrum

Requirements:

• SPF≥15

• Critical wavelength (CW)≥370nm

Products meeting both criteria can claim "Broad Spectrum." Others must warn they only prevent sunburn, not skin cancer or aging.

Critical wavelength (CW): The longest wavelength blocking 90% of UV. Higher CW values indicate broader UV protection spectrum.

3. 欧洲标准：UVA圆圈与Boots星级

• UVA圆圈：如果产品包装上有一个UVA字母外面画着圆圈，代表其临界波长≥370纳米，且UVA防护力至少达到SPF值的三分之一。

• Boots星级：用星级（一至五星）来标示UVA与UVB防护能力的均衡度。星级越高，当两者防护越均衡，越能同时防护UVA和UVB，能更全面抵抗紫外对皮肤的伤害。zui多为五星。

3. European Standard: UVA Circle & Boots Star Rating

• UVA Circle: Indicates CW≥370nm and UVA protection ≥1/3 of SPF value

• Boots Stars (1-5): Rates UVA/UVB protection balance. Higher stars mean more balanced protection against both UV types.

「防水防汗功能 / Water Resistance Claims」

1. 中国标准

• 抗水抗汗：产品通过40分钟的测试，可标注“防水防汗"，需注明时间不超过40分钟。

• you yue抗水：产品通过80分钟的测试，可标注“you yue抗水"，需注明时间不超过80分钟。

• 若浸泡后SPF值下降超过50%，则不得宣称具有防水功能。

2. 美国标注

一般标注为“Water Resistant"。

1. China Standards

• Water Resistant: Maintains SPF after 40min water immersion

• Very Water Resistant: Maintains SPF after 80min

Products losing >50% SPF after testing cannot claim water resistance.

2. US Standards

Labeled as "Water Resistant "

「其他标识 / Additional Label Terms」

• Safe-Eye Tech：产品通过验证测试，可在眼周使用，不易熏眼。

• Wet Skin：可在湿皮肤上直接涂抹，非常适合海边、泳池等场景。

• 12M：建议开封后12个月内用完。防晒剂稳定性会随时间下降，隔年的防晒霜防护效果会大打折扣，不建议继续使用。

• Safe-Eye Tech: Ophthalmologist-tested for eye area use

• Wet Skin Application: Can apply to damp skin

• 12M: Use within 12 months after opening for optimal efficacy

说到底，防晒可不是简单买个指数好的产品就万事大吉了。真正的秘诀在于“涂够量、勤补涂"，再搭配上帽子、墨镜这些硬防晒装备，才能做到有效的防晒。

记住这个挑选小窍门：

日常上班通勤：选择质地轻薄、不粘腻的，方便随时补涂。

户外运动、海边玩水：防水防汗功能是重中之重，一定要认准明确的抗水标识。

Ultimately, sun protection isn’t as simple as buying the product with the highest SPF and calling it a day. The real secret lies in applying a sufficient amount and reapplying it frequently, combined with physical protection like hats and sunglasses, to ensure complete safety.

Keep this selection tip in mind:

For daily commutes: Choose lightweight, non-sticky formulas for easy reapplication.

For outdoor activities or beach trips: Water and sweat resistance is crucial—always look for clear waterproof labeling.