What it is
In the register’s words: “Cyclopentasiloxane is the cyclic dimethyl polysiloxane.”
- EU register name (INCI)
- CYCLOPENTASILOXANE
- CAS number
- 541-02-6
- EC number
- 208-764-9
What the register lists it for
These are the uses the European Commission’s CosIng register lists for Cyclopentasiloxane in any cosmetic, hair roles first. They say why a maker might add it, not what it does in one formula, and they aren’t a safety rating.
- Hair conditioning
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The register’s hair role for ingredients that make hair feel softer, smoother or easier to comb. Most conditioners, masks and leave-ins list several.
Register definition: “Enhancing the appearance and feel of hair. Leaving the hair easy to comb, supple, soft and shiny and/or imparting volume, lightness, gloss, texture, etc.”
- Emollient
-
Oils, butters and similar ingredients that make a surface feel soft and smooth. On hair they coat the strand; many plant oils carry this role.
Register definition: “Acting as lubricants on the skin surface providing the skin with a soft and smooth appearance.”
- Solvent
-
Dissolves other ingredients. Water is the most common; some alcohols and glycols carry this role too.
Register definition: “Dissolving other components of cosmetics. Solvents are usually liquids (aqueous and nonaqueous).”
- Skin conditioning
-
The register’s broad role for ingredients that keep skin in good condition. On a hair label it often sits beside a hair role, or marks a plant oil or extract.
Register definition: “Maintaining the skin in good condition.”
Where it sits on each label
US labels list ingredients from most to least, except that those at 1% or less may follow in any order. A name near the top is a large part of the formula. A label doesn’t mark where the 1% point falls, so further down, the order says little about how much is in it.
- Rinse-out conditioners 1 label First five names: 1 of 1 Rinse-out conditioners without it
- Deep conditioners 1 label First five names: 0 of 1 Deep conditioners without it
- Stylers 2 labels First five names: 0 of 2 Stylers without it
- Heat protectants 1 label First five names: 0 of 1 Heat protectants without it
Every label, product by product (5)
- Mielle Pomegranate & Honey Moisturizing and Detangling Conditioner Rinse-out conditioner 3rd of 22 names
- The Doux THAT’S DEEP 5-Minute Deep Conditioner Deep conditioner 10th of 25 names
- Aussie Miracle Curls Frizz Free Curl Cream Styler 6th of 25 names
- TRESemmé Bouncy Curls Defining Mousse Styler 16th of 20 names
- Mielle Mongongo Oil Thermal & Heat Protectant Spray Heat protectant 21st of 28 names
Each line runs from the first name on a label to the last; a dot is where this ingredient sits. Makers change formulas now and then; if the list on your bottle differs, go by your bottle.
Your next step
Other hair conditioning ingredients on these labels
- Glycerin 131 labels
- Panthenol 72 labels
- Cocos Nucifera (Coconut) Oil 69 labels
- Behentrimonium Methosulfate 38 labels
- Caprylyl Glycol 37 labels
- Behentrimonium Chloride 34 labels
- Cocamidopropyl Betaine 34 labels
- Simmondsia Chinensis (Jojoba) Seed Oil 34 labels
Updated · The name, numbers and uses come from the European Commission’s CosIng entry (CC BY 4.0); we write the uses in US spelling and put the hair ones first. The labels are each maker’s own. The order rule is the FDA’s Cosmetics Labeling Guide. All our sources are on the Sources page.