迷思 1：室內不用擦防曬
「我整天都待辦公室，根本曬不到太陽。」
UVA 穿玻璃、藍光從螢幕來，室內也要防曬。
紫外線分 UVA 與 UVB:
- UVB：造成曬傷、皮膚癌，大部分被玻璃擋住。
- UVA：造成曬黑、皺紋、肝斑、長期 DNA 損傷，能穿透一般玻璃 50% 以上，所以靠窗座位、開車、室內仍會被曬。
近年研究也發現可見光（尤其藍光與紫光）會加重肝斑與深膚色族群的色素沉澱；手機 / 螢幕雖然強度低於陽光，但對已有色素問題的人仍要小心。建議靠窗工作 / 居家辦公族每天仍要擦防曬(SPF 30 以上含廣譜 UVA 防護）。
迷思 2：陰天 / 下雨可以省防曬
「今天又陰又冷，擦防曬太浪費了。」
陰天 UVA 仍可達晴天的 80%。
雲層擋住的是部分 UVB（讓你不那麼容易曬傷），但UVA 穿透雲層的能力很強，陰天 UVA 強度可達晴天 80%。如果你只在「曬到太陽很燙」才擦防曬，等於只防了一半的紫外線傷害。長期累積下來會看到老化、斑點、紋路加重。
迷思 3:SPF 越高效果越好
「SPF 100 是 SPF 50 的兩倍效果吧？」
SPF 30 已擋掉 ~ 97% 的 UVB,SPF 50 擋 ~ 98%,SPF 100 擋 ~ 99% — 邊際效益很小。
SPF 是對 UVB 的防護指數，不代表 UVA 防護(UVA 看 PA / PPD / 廣譜標示）。SPF 30 與 SPF 100 之間的實際差別只有 2-3 個百分點，但是使用習慣的影響遠大於 SPF 數字 — 大多數人實際擦的厚度只有實驗室測試厚度的 1/3，等於你的 SPF 50 在臉上實際大概只有 SPF 17。
關鍵不是 SPF 數字，是「擦夠厚 + 規律補擦」。日常臉部建議 SPF 30+ 廣譜防曬，擦約一個 5 元硬幣大小的量。
迷思 4：物理防曬一定比化學防曬好
「化學防曬有毒會被吸收進身體，物理才安全。」
兩者各有優缺，皮膚科醫師都用，沒有誰比較毒。
- 物理（無機）防曬：氧化鋅(zinc oxide)、二氧化鈦(titanium dioxide)。穩定、低敏、孕婦可用。缺點：質地較厚重、易泛白（亞洲膚色更明顯）、油性肌容易悶。
- 化學（有機）防曬:Avobenzone、Tinosorb、Mexoryl 等。質地清爽、透明、防護廣譜。少數成分（如 oxybenzone、octinoxate)對珊瑚礁不友善，夏威夷與某些國家已禁用，但近年新一代化學防曬劑(Tinosorb S/M、Mexoryl SX/XL、Uvinul A Plus)安全性與穩定性都很好。
「化學防曬被吸收進身體」是 2019 年 FDA 一篇研究後的網路恐慌，該研究只證實能驗到血中代謝物，並未證實有任何健康危害;FDA 至今仍將化學防曬劑列為合法可用。對絕大多數使用者來說，兩種都安全有效，挑你皮膚耐受、會持續使用的就好。
迷思 5：一天擦一次就夠
「早上出門擦了，撐一整天沒問題。」
流汗、擦臉、流油、口罩摩擦都會讓防曬掉，需要補擦。
Studies show that 防曬擦在皮膚上 2-4 小時後，實際保護力降低 50% 以上（因為被汗 / 油 / 摩擦帶走）。下午仍在戶外或靠窗位置者，建議：
- 用防曬噴霧、棒狀防曬、防曬粉、防曬蜜粉來補擦，不會破壞底妝
- 每 2-3 小時補一次
- 下水或大量流汗後立刻補擦
純室內坐辦公室的人不需要每幾小時補，但出去吃午餐前 / 下班前可以再補一次。
迷思 6：防曬乳一定會堵塞毛孔長痘
「我擦了防曬就冒一堆痘痘，都是防曬害的。」
老一代厚重防曬會，新一代「無油」「不致粉刺」配方不會。
市面上很多「oil-free」、「non-comedogenic（不致粉刺）」、「痘痘肌專用」的防曬，使用矽質或水性配方，實測致粉刺風險很低。如果你擦了會冒痘，先試：
- 換 gel 質地或 liquid 質地（別用厚重霜狀）
- 選成分含 niacinamide / azelaic acid 的防曬
- 確認不是底妝產品（粉底、定妝粉、隔離霜）悶痘而誤怪到防曬上
- 晚上記得卸防曬
迷思 7：深膚色不會曬黑曬傷
「我本來就比較黑，反正曬不黑啦。」
深膚色雖然天生有較多 melanin 保護，仍會曬傷、皮膚癌、明顯加重肝斑與痘印。
美國皮膚科醫學會的觀察：
- 深膚色族群的皮膚癌（尤其黑色素瘤）確診時往往較晚期、預後較差，因為「以為不會得」就不防曬。
- 深膚色族群最在意的肝斑、痘印、發炎後色素沉澱幾乎都會被陽光加重 — 沒做防曬美白藥膏白擦。
結論：不論膚色，防曬都該天天擦。深膚色族群尤其建議使用含氧化鐵(iron oxide)的防曬，氧化鐵對可見光與藍光也有防護效果，改善肝斑特別有用。
迷思 8：全身共用同一支防曬
「臉跟身體一支搞定省事又省錢。」
原則上可以，但臉、身體、嘴唇、眼周、嬰幼兒最好分開。
- 身體防曬：質地厚、量大、價格低，可大膽用。
- 臉部防曬：質地清爽、不油膩、不致粉刺，常含 niacinamide / 抗氧化劑。
- 嘴唇：選 SPF 護唇膏（無香料、無薄荷），嘴唇皮膚薄、紫外線易致老化與唇癌。
- 眼周：刺激性低的物理防曬棒最好，避免化學防曬流入眼睛刺癢。
- 6 個月以下嬰兒：不建議使用防曬，以衣物 / 帽 / 撐傘為主；6 個月以上選嬰幼兒專用、純物理性、無香料防曬。
結語 — 一句話記住
每天擦、擦夠厚、規律補擦、SPF 30+ 廣譜防護。挑一支自己會持續擦的（質地舒服 + 預算 OK)，比追求最高 SPF 重要 100 倍。
延伸閱讀：有色素沉澱困擾？外用酸類完整衛教 介紹杜鵑花酸與果酸如何淡化痘印與肝斑。痘痘成人型？痘痘 8 大迷思 與 口服 A 酸完整衛教。
常見問題（PTT / Dcard 上常被問的）
Q
防曬乳 PTT / Dcard 推薦的牌子如何挑？
A網路討論度高的：安耐曬(Anessa)、理膚寶水(La Roche-Posay Anthelios)、怡麗絲爾、Heliocare 360、艾比安(Albion)、Neutrogena Ultra Sheer。挑選重點不是品牌：① 廣譜（SPF 30+ PA+++ 以上）② 含氧化鐵 iron oxide（防可見光，肝斑必備）③ 質地能規律補擦的。售價 NT$ 400-2000 都有實用品。
Q
防曬 SPF 50 跟 SPF 30 差很多嗎？
ASPF 30 已擋掉 97% UVB,SPF 50 擋 98% — 邊際效益 1%。實際擦的厚度(2 mg/cm²)才是關鍵，多數人實際只擦 1/3 厚度，導致 SPF 50 變成「實質 SPF 17」。挑能規律擦、不油不悶、能補擦的 SPF 30+ 比追求 SPF 50+ 重要。
Q
物理性 vs 化學性防曬哪個好？
A沒有絕對贏家。物理性(Zinc oxide、Titanium dioxide)穩定、敏感肌可用、孕婦較安心，但傳統質地較厚白。化學性(Octinoxate、Avobenzone、Octisalate、Tinosorb)質地較佳，但部分舊款成分(Oxybenzone、Octinoxate)有環境疑慮、極少數人接觸過敏。新款混合型(Tinosorb S/M、Mexoryl)質地與穩定性都好。
Q
防曬乳要不要卸妝？
A純化學性防曬通常溫和洗面乳就能洗掉。物理性、含氧化鐵、防水抗汗款、有色防曬建議用潔顏油或卸妝乳輕柔卸除。指引：擦了之後皮膚摸起來「卡卡」、洗完還有殘留感，就需要卸妝。
Q
小孩、孕婦防曬怎麼挑？
A6 個月以下嬰兒避免擦防曬，以遮蔽和避光為主。6 個月以上+孕婦建議用純物理性防曬(Zinc oxide、Titanium dioxide)，避開 Oxybenzone、Octinoxate（內分泌干擾疑慮）。孕婦肝斑活化，室內也要擦含氧化鐵的防曬。
參考資料
- Lim HW, et al. AAD position statement on sun protection.J Am Acad Dermatol. 2018;78(2):e25-e26. 「來源」
- Matta MK, et al. Effect of sunscreen application on plasma concentration of sunscreen active ingredients (FDA MUsT study).JAMA. 2020;323(3):256-267. 「來源」
- FDA. Final Rule on Sunscreen Drug Products for OTC Human Use (Deemed Final Order, 2021).[FDA]
- Lyons AB, et al. Photoprotection beyond UV — visible light and infrared.J Am Acad Dermatol. 2021;84(5):1393-1397. 「來源」
- Schalka S, Steiner D. Brazilian consensus on photoprotection. An Bras Dermatol. 2014;89(6 Suppl 1):1-74. 「來源」
- Lim HW, et al. Adverse effects of ultraviolet radiation. J Am Acad Dermatol. 2017;76(5):866-875. 「來源」
- Castanedo-Cazares JP, et al. Iron oxide-containing sunscreens for melasma. Photodermatol Photoimmunol Photomed. 2014;30(1):35-42. 「來源」
- Pasquali P, et al. Iron oxide-containing sunscreens are effective for melasma in real-world conditions.J Cosmet Dermatol. 2020;19(3):671-675. 「來源」
- UpToDate: Selection of sunscreen and sun-protective measures. 「來源」
Myth 1: No need for sunscreen indoors
"I'm sitting in the office all day — I don't need sunscreen."
UVA penetrates glass. Indoor windows, desks by windows, and car commutes still expose you to ~50% of outdoor UVA dose.
UVB is largely blocked by glass, but UVA passes through window glass freely. Long-term, this contributes to photoaging (wrinkles, sagging, pigmentation) and worsening of melasma. Visible light and blue light from screens also drive pigmentation in darker skin types and melasma sufferers — these aren't blocked by ordinary sunscreens unless they contain iron oxide.
Practical rule: if you sit near a window or commute by car/scooter for any meaningful time, daily SPF 30+ broad-spectrum is worth it. Tinted sunscreens with iron oxide add visible-light protection.
Myth 2: Cloudy or rainy days = skip sunscreen
"It's not sunny today, why bother?"
Up to 80% of UVA penetrates clouds. Cloudy ≠ UV-free.
Clouds block some UVB (so you're less likely to feel a sunburn), but UVA is barely affected. If you only protect when "the sun is bright and hot," you're missing half the cumulative damage. Over years this shows up as photoaging, melasma flares, and deeper pigment marks.
Myth 3: Higher SPF is always better
"SPF 100 must be twice as effective as SPF 50."
SPF 30 already blocks ~97% of UVB; SPF 50 ~98%; SPF 100 ~99%. Marginal benefit is tiny.
SPF measures UVB protection only — UVA protection comes from PA / PPD or "broad spectrum" labeling. The difference between SPF 30 and SPF 100 is just 2-3 percentage points, but application habits matter far more than the SPF number. Most people apply only ~⅓ of the lab-tested thickness, so your SPF 50 effectively performs at ~SPF 17 on your face.
The key isn't the SPF number — it's "apply enough + reapply regularly." Daily face: SPF 30+ broad-spectrum, about a 5-NTD-coin's worth.
Myth 4: Physical sunscreens are always safer than chemical ones
"Chemical sunscreens are toxic and absorbed into the body — only physical is safe."
Both have pros and cons. Dermatologists use both. Neither is "toxic."
- Physical (inorganic): zinc oxide, titanium dioxide. Stable, low-allergenic, pregnancy-safe. Cons: thicker texture, may leave a white cast (more obvious on Asian skin tones), can feel heavy on oily skin.
- Chemical (organic): avobenzone, Tinosorb, Mexoryl, etc. Lighter texture, transparent, broad-spectrum. A few legacy ingredients (oxybenzone, octinoxate) are coral-reef-unfriendly and banned in Hawaii and some Pacific nations, but newer chemical filters (Tinosorb S/M, Mexoryl SX/XL, Uvinul A Plus) are very safe and stable.
The "chemical sunscreens are absorbed into the body" panic stemmed from a 2019 FDA pharmacokinetic study showing measurable blood levels after heavy use; the study did not show any health harm. The FDA continues to consider chemical sunscreens safe and effective for general use.
Myth 5: One application in the morning lasts all day
"I put sunscreen on at 7 AM, I'm covered until evening."
Sweat, oil, mask friction, and touching your face all degrade sunscreen. Reapplication is required.
Studies show that 2-4 hours after application, on-skin SPF drops by 50% or more. For people outdoors or near windows in the afternoon:
- Use spray, stick, or powder sunscreen for top-ups without disrupting makeup
- Reapply every 2-3 hours
- Reapply immediately after swimming or heavy sweating
If you're truly indoors all day at a desk, you don't need to top up every few hours — but a midday or pre-evening reapply before going outside helps.
Myth 6: Sunscreen always clogs pores and causes acne
"Every time I wear sunscreen I break out — sunscreen causes acne."
Old-formula heavy sunscreens did. Modern oil-free, non-comedogenic formulas don't.
Many sunscreens are now formulated as oil-free, non-comedogenic, or acne-prone-skin specific with silicone or water-based bases. These have very low pore-clogging risk. If you break out:
- Switch to a gel or fluid texture (avoid heavy creams)
- Pick formulas with niacinamide or azelaic acid
- Check whether the actual culprit is your foundation, setting powder, or BB cream being mistakenly blamed on sunscreen
- Cleanse off sunscreen at night
Myth 7: Darker skin doesn't burn or get skin cancer
"My skin is already dark — UV won't affect me."
Darker skin has more melanin protection, but still burns, still develops skin cancer, and still develops worsened melasma and post-inflammatory pigmentation.
Per the American Academy of Dermatology:
- Skin cancer (especially melanoma) in darker skin is often diagnosed at later stages with worse outcomes, because patients assume they're not at risk and skip sunscreen and skin checks.
- Conditions that bother darker skin most — melasma, post-inflammatory hyperpigmentation, acne marks — are aggravated by sun exposure. Skipping sunscreen makes lightening creams essentially useless.
Bottom line: regardless of skin tone, daily sunscreen matters. Darker skin types especially benefit from iron-oxide-containing sunscreens, which block visible light and are particularly helpful for melasma.
Myth 8: One sunscreen for the whole body
"One bottle for face and body — saves time and money."
Generally fine for adults, but face, body, lips, eye area, and infants ideally use different formulas.
- Body sunscreen: thicker texture, large volume, lower price point — apply liberally.
- Face sunscreen: lightweight, non-greasy, non-comedogenic; often contains niacinamide or antioxidants.
- Lips: SPF lip balm (fragrance-free, mint-free); lip skin is thin and vulnerable to photoaging and lip cancer.
- Eye area: low-irritation physical sunscreen sticks are best — chemical sunscreens running into the eyes burns.
- Infants under 6 months: avoid sunscreen — use clothing, hats, and shade. 6+ months: pick infant-specific, pure physical, fragrance-free.
Bottom line — one sentence
Apply daily, apply enough, reapply regularly, SPF 30+ broad-spectrum. Picking one you'll actually use consistently (comfortable texture + within budget) matters 100× more than chasing the highest SPF.
Further reading: dealing with pigmentation? See Topical Acids Complete Guide for how azelaic acid and AHA can fade dark spots. Adult acne? See 8 Acne Myths and Oral Isotretinoin Complete Guide.
Frequently asked (PTT / Dcard style)
How to pick a sunscreen brand?
Popular picks: Anessa, La Roche-Posay Anthelios, Elixir, Heliocare 360, Albion, Neutrogena Ultra Sheer. The brand isn't the point — what matters： ① broad spectrum (SPF 30+ PA+++)， ② contains iron oxide if you have melasma， ③ a texture you'll actually reapply. Quality picks exist at every price point from NT$ 400 to NT$ 2000.
Big difference between SPF 50 and SPF 30?
SPF 30 blocks 97% of UVB; SPF 50 blocks 98% — a 1% gap. Real-world thickness (need 2 mg/cm²) matters more — most people apply only ⅓ of the test amount, making SPF 50 perform like SPF 17. Pick a SPF 30+ that you'll reapply rather than chasing SPF 50+ you skip.
Physical vs chemical sunscreens — which is better?
No outright winner. Physical (zinc oxide, titanium dioxide) is stable, suitable for sensitive skin, safer in pregnancy, but classic formulas leave a white cast. Chemical (octinoxate, avobenzone, octisalate, Tinosorb) has lighter textures but some legacy ingredients (oxybenzone, octinoxate) raise environmental concerns, and rare individuals get contact allergy. Newer hybrid formulas (Tinosorb S/M, Mexoryl) offer the best of both.
Do I need makeup remover for sunscreen?
Pure chemical sunscreens usually wash off with a gentle cleanser. Physical, iron-oxide-containing, water-resistant, or tinted formulas benefit from cleansing oil or balm. Rule of thumb: if your skin still feels coated or "sticky" after washing with face wash, use makeup remover.
Sunscreen for kids and pregnant women?
Under 6 months: avoid sunscreen — rely on shade, clothing, hats. Over 6 months and pregnancy: pure physical sunscreens (zinc oxide, titanium dioxide) are first choice; avoid oxybenzone and octinoxate (endocrine-disruption concerns). Pregnancy-related melasma flares — wear iron-oxide tinted sunscreen even indoors.
References
- Schalka S, Steiner D. Brazilian consensus on photoprotection. An Bras Dermatol. 2014;89(6 Suppl 1):1-74. [Source]
- Lim HW, et al. Adverse effects of ultraviolet radiation. J Am Acad Dermatol. 2017;76(5):866-875. [Source]
- Castanedo-Cazares JP, et al. Iron oxide-containing sunscreens for melasma. Photodermatol Photoimmunol Photomed. 2014;30(1):35-42. [Source]
- UpToDate: Selection of sunscreen and sun-protective measures. [Source]
