Sunday, September 10, 2017

[Repost]: SPF/PA/UVA/UVB

Title:  SPF and PA. Do You KNOW your sunscreen?

From: Beautyficient

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Sunburn

When exposed to the sun,

our bare skin will eventually get

red, swollen and feel painful because

the internal structures are damaged.

This is commonly known as sunburn.

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UV

The main culprit?

Ultra Violet rays or UV rays from the sun.

UV rays can be further split into

UVA, UVB and UVC rays

which all cannot be detected by

the naked eye.

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UVA

The Ageing ray and

main reason behind sun related skin cancers.

It destroys the vitamin A in our skin and

also indirectly causes DNA damage.

Makes up 98.7% in UV rays.

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UVB

The Sunburn ray.

This ray directly causes

DNA damage to skin cells.

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UVC

The most powerful out of all three rays,

but most often filtered so

there’s almost none of it when

it reaches our skin.

Damages DNA directly too.

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All three rays

UVA, UVB and UVC damages the

collagen fibers in our skin which is

responsible for keeping our skin young,

as collagen contributes to the

elasticity of our skin.

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So, it is reasonably clear that

UV rays contribute significantly to

accelerate ageing of our skin as well as

any part of the body exposed to it,

such as our eyes.

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SPF

Stands for Sun Protection Factor.

It is a way of expressing

how effective a sunscreen is at

protecting against UVB rays specifically.

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The numerical digit following SPF indicates

how much time you’ll be able to

withstand exposure to the sun before

burning up in sunburn frenzy.

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For an example,

If Brad Pitt took 15 minutes to reach

the state of being sun burnt,

an SPF30 sunscreen will delay his time to

achieve a sunburn by 30 times more.

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A higher SPF will of course give

better protection against UVB, but usually,

SPF 30 would be sufficient for daily use.

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For folks with lighter skin,

a higher SPF such as SPF 50 would be

more effective as they burn much faster

compared to people with darker skin.

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PA

Abbreviation for Protection Grade of UVA

established by the Japanese.

It basically informs users of

the level of protection towards UVA rays.

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PA+

means the sunscreen provides

some protection against UVA rays,

PA++

indicates moderate protection while

PA+++

shows very good protective abilities

against UVA rays.

Since UVA causes long term skin damage,

it is therefore advisable to go for

sunscreens with the highest PA rating.

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Broad Spectrum

Sunscreens that provide both

UVB and UVA protection

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Sunblock vs sunscreen

Sunblock provides better protection from

UV rays compared to sunscreen as

they contain a more opaque formulation,

hence, require less bouts of reapplying.

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The chemicals in sunscreens breakdown at

a faster rate under sun exposure so

are comparatively,

a little less effective than sunblocks.

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Apart from that,

sunscreens are better suited for daily use while

sunblocks are best for sports or activities

requiring higher exposure to UV rays.

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Typically, sunscreens today are made to

suite the conditions of the wearer’s skin.

Sunscreens come in moisturizing, mattifying,

make up base, color correcting,

plumping, anti ageing, fragrance free and

many more varieties of formulations.

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In short

Also, the sunscreen should be

a broad spectrum formula with

an adequate SPF and

the highest PA rating possible.

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As a guideline,

SPF 30 PA+++ for daily wear,

SPF50 PA+++ for outdoor activities or

for folks living nearer to the equator.

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Title: Chemical Vs. Physical Sunscreens: Pros And Cons

From: Renee Rouleau

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Physical sunscreens

contain active mineral ingredients,

such as titanium dioxide or zinc oxide,

which work by sitting on top of the skin to

deflect and scatter damaging UV rays

away from the skin.

They are often referred to as physical blockers.

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Pros of physical sunscreens

Offers protection against both

UVA and UVB rays and

is naturally broad spectrum

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Protects from the sun as soon as it’s applied

no wait needed

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Lasts longer when in direct UV light

(but NOT when doing physical activities

that cause the skin to get wet or sweat)

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Less likely to cause

a stinging irritation on the skin,

making it better for sensitive skin

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Better for those with heat-activated skin

(like those with rosacea and redness) since

it deflects the heat and energy

given off by the sun away from the skin

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Less likely to be pore-clogging,

making it ideal for blemish-prone skin types

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Longer shelf life

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Cons of physical sunscreens

Can rub off, sweat off and rinse off easily,

meaning more frequent reapplication

when outdoors is needed

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May leave a white-ish cast on the skin,

making some formulas incompatible for

medium to dark skin tones

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May be too chalky and opaque for

daily use under makeup

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Can create an occlusive film,

which results in increased perspiration

during physical activities and, therefore,

causes it to wear off more quickly

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Can be thicker,

which will require more effort to rub in

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Can cause white drips to

show on the skin when sweating

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Can be less protective if

not applied generously and accurately

since UV light can get between

the sunscreen molecules and

get into the skin

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Chemical sunscreens

contain organic (carbon-based) compounds,

such as oxybenzone, octinoxate,

octisalate and avobenzone,

which create a chemical reaction and

work by changing UV rays into heat,

then releasing that heat from the skin.

They are often referred to as

chemical or organic absorbers.

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Pros of chemical sunscreens

Tends to be thinner and, therefore,

spreads more easily on the skin,

making it more wearable for daily use

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Less is needed to protect the skin because

there is no risk of no spaces between

the sunscreen molecules after application

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Formula is easier to

add additional treatment ingredients,

such as peptides and enzymes,

which offer other skin benefits

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Cons of chemical sunscreens

Can possibly cause an increase in

existing brown spots and discoloration

due to a higher internal skin temperature

(Yes, over-heated skin can make

brown spots worse. Read why here.)

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Requires about 20 minutes

after application before it begins to work

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Increased chance of irritation and stinging

(especially for those who have dry skin with

a damaged moisture barrier)

due to the multiple ingredients combined

in order to achieve broad spectrum

UVA and UVB protection

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The higher the SPF

(such as formulas of SPF 50 or greater),

the higher the risk of irritation for

sensitive skin types

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The protection it offers gets used up

more quickly when in direct UV light,

so reapplication must be more frequent

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Increased chance of redness for

rosacea-prone skin types because

it changes UV rays into heat

which can exacerbate flushing

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May clog the pores for oily skin types

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Can cause stinging if

it drips into the eyes from sweat

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When it comes to sunscreen,

it’s hard to say which one is

truly the best for your skin

since all formulas are not created equal.

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Which type of sunscreen offers

the best UVA and UVB protection?

This is a huge debate among scientists.

Currently, the FDA is taking steps to

establish new standards of measuring

the effectiveness of sunscreens more accurately

in an effort to educate consumers on

how best to prevent the detrimental effects of

exposure to UV radiation.

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For now, however,

both physical and chemical sunscreens

will do a great job at protecting your skin,

as long as you are applying them

generously every morning and

reapplying throughout the day.

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Title: 夏日防曬論 豈止讀懂 UVA、UVB 那麽簡單

From: Harper Bazaar HK

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新商品法例禁誇大
由去年起,"Water Proof" 或 "Sunblock" 等字眼

已消失於美國出品的防曬產品。

皆因去年一月,美國 FDA(美國食品及藥物管理局)

對防曬產品作出新規定:

防曬產品只可標籤為 "Water Resistant",

不能再用 "Water Proof",

因為經測試證實沒可能 100% 防水,

且 "Water Resistant" 時間

只許標示為 40 或 80 分鐘,

因為防曬時間根本無法超過 80 分鐘;

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產品需同時抵擋 UVA 及 UVB,

才可歸類為防曬產品(Broad Spectrum 類別);

防曬產品也不能標籤為 "Sunblock",

因為沒可能 100% 阻隔紫外線,

只可稱為 "Sunscreen";

須蘊含防紫外線(UV)成分的產品才

可歸類為 "Anti-aging",

簡單而言就是要產品之名如實。

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雖然這些老實標籤只限

美國出品的防曬產品,

但對女性而言,總算多個誠實選擇渠道。

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外國有新例規管防曬產品的標籤,香港亦然,

《2012 年商品說明(不良營商手法)(修訂)條例》

於 2013 年 7 月 19 日日正式生效,

限制商品說明都不能有

誤導性遺漏、餌誘式廣告宣傳等。

那些年有令人無法抗拒的魔力字眼:

「最防曬」、「最受歡迎」及「最暢銷」,

統統說再見,防曬產品同時也告別

絕對百分百防曬等用語。

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不過對於產品的標籤,

則沒進一步限制規管,

所以相對消費者而言,分別不大。

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系數強弱按需要

防曬產品必定列有 SPF 及 PA 值,

探究兩者意義前,

先要明白紫外線分為

UVA、UVB 及 UVC 三種,

大部分 UVC 會被臭氧層阻隔,

只餘 UVA 和 UVB 投射地面,影響皮膚,

前者可直達真皮層,破壞細胞,

長年累月造成肌膚老化鬆弛、

皺紋及黑色素沉澱;

UVB 的能量比 UVA 強,導致即時性傷害,

如暗沉、變紅、眼膜炎及皮膚發痛變乾,

防曬產品的任務就是阻隔 UVA 和 UVB。

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SPF(Sun Protection Factor)

是由美國醫生指定的防曬指標,

用來衡量會曬傷肌膚的 UVB 防曬度,

如防曬度數 SPF15、30 跟 50

分別可阻隔約 94%、97% 及 98% 的紫外光;

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PA(Protection Factor of UVA)

則是對 UVA 的防護能力,

PA 值可分為

PA+、PA++、PA+++、PA++++ 四種,

+ 號愈多,代表對紫外線 UVA 的防護力愈高,

簡化點就是延緩皮膚曬黑的指數,

例如 PA+ 可延緩皮膚曬黑 2 至 4 倍、

PA++ 是 4 至 8 倍,

PA+++ 則可達 8 倍以上。

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選購防曬產品並非

追求越高數值、越多加號為好,

因為防曬系數越高,

代表所含的化學物相對的多,

隨時未阻隔陽光,先刺激肌膚。

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一般戶活動,

建議選擇 SPF15,PA+ 的防曬已足夠;

若同陽光玩遊戲,

就要選擇 SPF35 以上、PA++ 或以上的防曬產品,

並謹記在流汗後補塗。

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想防曬產品功效發揮最好,

就要在出門前最少半小時前塗搽,

而防曬系數亦非一般加數,

縱然現今底霜、粉底都具防曬功能,

但防曬系數並不能累積計算,

譬如使用了 SPF15 的防曬面霜,

再用 SPF30的防曬乳,

只相等於塗上 SPF30 的防曬。

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物理性防曬最安全

防曬產品可以分出無限多類別,

乳液狀、噴霧裝,

甚至具調色等多功能性,

但最基本且必須要知的,

就是為分化學性及物理性。

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化學性原理是 (Chemical)

經皮膚吸收化學物質來抵禦紫外線,

優點為淸爽不稠,

但較容易引起過敏,皮膚易敏感者慎用;

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物理性則是 (Physical)

在皮膚上形成一反射性層,

把紫外光反射,猶如為皮膚穿上防曬保護衣,

阻隔、折射、及散射紫外光,

大部分的物理性防曬產品都是

採用天然礦物提取成分,

如氧化鋅(Zinc Oxide)及

二氧化鈦(Titanium Dioxide),

加上不被皮膚吸收,不易引發皮膚敏感,

適合敏感性皮膚人士和肌膚較嫩的兒童使用。

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但由於二氧化鈦和氧化鋅是礦物粉體,

須與植物或礦物油、水等成分配合,

才能製出乳霜,

故物理性防曬的質感都較化學性油膩,

且謹記要以卸妝產品徹式清除。

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