CYCLOTETRASILOXANE
Commonly Found In
Overview
Cyclotetrasiloxane (D4) is a cyclic silicone (octamethylcyclotetrasiloxane) used in cosmetics as a lightweight, fast-evaporating emollient and solvent. The EU restricts D4 to below 0.1% in all leave-on cosmetics due to its classification as a persistent, bioaccumulative, and toxic (PBT) substance with aquatic toxicity concerns. Japan and the US allow broader use.
Also known as: D4, octamethylcyclotetrasiloxane, OMCTS
Key Benefits
Studies suggest D4 provides a silky, non-greasy skin feel and excellent spreadability. It is not associated with skin harm at cosmetic concentrations; EU restrictions are driven entirely by environmental PBT concerns rather than human safety.
Supporting Research
- β’ EU ECHA PBT assessment (2015): D4 classified as PBT substance; concerns for aquatic ecosystems, not human skin safety
- β’ CIR Expert Panel: D4 assessed as safe for human use at cosmetic concentrations
Skin Compatibility Ratings
Comedogenic Rating
Non-comedogenic; evaporates from skin surface
Source: CIR Expert Panel
Irritancy Rating
Very low irritancy to human skin at cosmetic concentrations
Source: CIR Expert Panel
Typical Use Concentration
Range
1β20% (outside EU restriction)
Optimal
5β15%
EU: <0.1% in leave-on (practically banned). Japan and US: no specific cosmetic restriction.
Works Well With / Avoid
Works Well With
EU Annex II/1388: restricted to <0.1% in leave-on cosmetics (effectively banned). EU/UK ban is environmental, not human safety-driven. Japan and US allow normal formulation levels.
Commonly Found In
Global Regulation Summary
Overview of current status across major international markets.
Detailed Regional Status
| Region | Status | Max Conc. | Conditions | Source |
|---|---|---|---|---|
| πͺπΊ EU | Banned | - | - | Official β |
| πΊπΈ USA | Allowed | - | - | Official β |
| π―π΅ Japan | Allowed | - | - | Official β |
| π°π· Korea | Unknown | - | - | Official β |
| π¬π§ UK | Banned | - | Follows EU regulations (II/1388) | Official β |
π Why Regulations Differ
D4 is restricted in EU/UK leave-on cosmetics due to PBT/vPvB environmental classification (ECHA 2015, Regulation 2018/1139). Japan and US have not adopted equivalent environmental-driven cosmetic restrictions. The restriction is environmental, not based on skin safety concerns.
Recent Regulatory Changes
- β’ EU Regulation 2018/1139: D4 restricted to <0.1% in leave-on cosmetics, effective January 2020
Regulation Analysis
Regional Agreement
Banned in EU, UK but allowed in USA, Japan.
Category Comparison
There are 174 ingredients in the HAIR CONDITIONING category. 99% are banned in at least one major market.
Strictness Ranking
πΏ Natural Sources
Synthetic silicone compound. Does not occur naturally.
π How It's Made
Produced by hydrolysis of dimethyldichlorosilane followed by cyclization. Part of the cyclomethicone family (D4, D5, D6).
π Uses in Cosmetics
Used in hair products and deodorants as a lightweight silicone that evaporates quickly without leaving residue. The EU restricted it in leave-on products to 0.1% since 2020 due to environmental concerns.
π¬ Other Applications
Industrial silicone polymer production, medical device coatings, and specialty solvents.
π‘ Fun Facts
- β’ EU restricted D4 and D5 in leave-on cosmetics to 0.1% in 2020 due to bioaccumulation and harm to aquatic life concerns
- β’ Canada classified D4 as toxic to the environment in 2008, one of the first countries to regulate cyclic siloxanes
- β’ D4 is a volatile silicone - it evaporates quickly, which is why it's used in products where silky feel without residue is desired
Related Skin Concerns
Data Sources
- β’ EU Regulation 2018/1139 β D4 restriction in leave-on cosmetics
- β’ ECHA PBT assessment for D4 (octamethylcyclotetrasiloxane)
- β’ CIR Expert Panel β Safety Assessment of Cyclomethicone/D4
Last data verification: 2026-04-12
Related Ingredients
CYCLOMETHICONE
CATALASE
DIBUTYL PHTHALATE
DICHLOROMETHANE
DIETHYLHEXYL PHTHALATE
HYDROLYZED HAIR KERATIN
Learn More
Frequently Asked Questions
Why is CYCLOTETRASILOXANE banned in the EU but allowed in the US?
The EU follows a precautionary principle, banning CYCLOTETRASILOXANE under II/1388 due to potential safety concerns. The US FDA has not found sufficient evidence to prohibit its use, allowing it under different safety assessment standards. This reflects differing regulatory philosophies between the two regions.
Why is CYCLOTETRASILOXANE banned in the EU but allowed in Japan?
The EU prohibits CYCLOTETRASILOXANE (II/1388) based on their strict safety criteria. Japan's Ministry of Health, Labour and Welfare (MHLW) has evaluated the ingredient and permits its use, potentially with different safety data or usage conditions.
What is CYCLOTETRASILOXANE used for in cosmetics?
CYCLOTETRASILOXANE is primarily used for hair conditioning in cosmetic products. It also serves as skin conditioning - emollient, solvent. The ingredient is commonly found in various cosmetic and personal care products.
Which countries regulate CYCLOTETRASILOXANE?
CYCLOTETRASILOXANE is banned in EU, UK. The ingredient is freely allowed in JP, US.
Are there alternatives to CYCLOTETRASILOXANE?
Due to regulatory restrictions on CYCLOTETRASILOXANE, cosmetic manufacturers often use alternative ingredients with similar functions. For hair conditioning, alternatives may include other approved ingredients in the same category. Consult product labels for specific formulations, and look for products compliant with your region's regulations.
Disclaimer
The information on this website is for educational and informational purposes only and is not intended as medical advice. While we strive for accuracy based on official government databases, cosmetic regulations change frequently. Always consult with a qualified professional or refer to the latest official regulatory documents for compliance. We are not responsible for any actions taken based on the information provided here.