日文：シクロペンタシロキサン

最重要的一点是，环状硅油，特别是环戊硅氧烷(D5)和环丁硅氧烷(D4,用在化妆品行业中较少)，可能会对母乳的产生有影响，有可能会想起婴儿的一些健康问题。至于有多大的严重性，目前还没有确切的证据，并且有一些相关争论在里面。目前加拿大政府已将环戊硅氧烷列为毒性化学成分之一，要求使用这个成分的化妆品公司去申报安全性及用量以便 更好的监管。

揮發性成分，借膚溫蒸散，不會造成堆積(取自張麗卿 博客分享)

矽能為肌膚或毛髮創造絲滑質感，也會在肌膚上形成一層如塑膠般的薄膜，進而瓦解肌膚釋放毒素的能力，並使刺激物質阻塞肌膚及毛孔，此外，矽是屬於生物無法分解的成分。一般標籤可能會將矽列為：環戊矽氧烷 (cyclopentasiloxane)、矽靈 (dimethicone) dimethicone copolyol.與二甲基矽氧烷共聚物 (dimethicone copolyol)

邱品齊醫師他在留言版回應說奇時保養品&洗髮精的矽靈都是不會阻塞毛孔的
矽靈在洗髮精不建議是因為它帶來的柔順感會讓人誤會，以為髮質很好
而忽略真正的護髮，同時也因為矽靈包覆的特性讓後續護髮吃不進去

而矽靈在保養品可能導致部分成分進不去(揮發性矽靈不會)
但也沒有阻塞毛孔的風險
且矽靈的密封性有很好的鎖水保濕效果
可以發現肌研濃極潤.水之印彈力霜都有加，且成分很前面

所以我對矽靈的評價很中性，不好不壞
但我洗髮精不會挑有矽靈的
潤髮沒關係，護髮盡量不要
保養品盡量不要(有點難度)，揮發性矽靈就沒差，像雅頓膠囊
化妝品有矽靈反而很喜歡
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環戊矽氧烷這個成分的作用是營造一種不油膩好吸收的假象，如果看到他排前的位置，用的時候不會要被好吸收的假象蒙蔽。

是一种顺滑剂、溶剂、毛发调节剂。常用于洗发、护法产品。会干扰人体内分泌系统。

CANCER CONCERN - One or more animal studies show tumor formation at moderate doses
https://www.ewg.org/skindeep/ingredient/701741/CYCLOPENTASILOXANE/

silicone so too thick to be absorbed in to skin.

Emollients act as a barrier, slowing down trans-dermal water loss. It only prevents moisture from escaping. silicones, mmethionine and dimethicone

Long term occlusion prevents the skin from recognizing the need to repair itself.

Commission Regulation (EU) 2018/35 of 10 January 2018
Shall not be placed on the market in wash-off cosmetic products in a concentration equal to or greater than 0,1 % by weight of either substance, after 31 January 2020.
http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=uriserv:OJ.L_.2018.006.01.0045.01.ENG&toc=OJ:L:2018:006:TOC

"Recently many ingredients have been restricted in cosmetic products, among others: Cyclopentasiloxane (D5) and Cyclotetrasiloxane (D4). Both of them are silicones, and they are used to protect the skin and to retain moisture."
"Cyclopentasiloxane (D5) can also be harmful to the environment."
"What do the Manufacturers need to do?

Make sure that the raw materials supplier provides you with Cyclopentasiloxane (D5) with the highest purity (99%) and that it does not contain Cyclotetrasiloxane (D4)
As a precautionary measure – plan to reformulate rinse-off cosmetic products with Cyclopentasiloxane by decreasing the amount until up to 0,1%, or by replacing it with another type of silicone"

http://obeliscosmetics.net/cyclopentasiloxane-d5-and-cyclotetrasiloxane-d4-restricted-in-the-eu/