Structural formula of decamethylcyclopentasiloxane, D5


What is it?

“Cyclomethicones  are a group of methyl siloxanes, a class of liquid silicones (cyclic polydimethylsiloxane polymers).” – Cyclomethicone wiki

Cyclomethicone dangers

This substance belongs to the groups:

Cyclomethicone is a generic group name for chemicals as:

  • Octamethylcyclotetrasiloxane (D4)
  • Cyclotrisiloxane (D3)
  • Cyclopentasiloxane (D5), Decamethylcyclopentasiloxane,  Cyclomethicone 5
  • Cyclopentasiloxane (D6)
  • Cycloheptasiloxane (D7)

So, is cyclomethicone safe as an ingredient?

This is how three mayor players have classified the chemical class:

The Swedish Society for Nature Conservation (SSNC) list cyclomethicone as an endocrine disruptor.

The European Chemicals Agency (ECHA) identifies that the substance

may be fatal if swallowed and enters airways, is toxic if inhaled, is harmful to aquatic life with long-lasting effects, is a flammable liquid and vapor and is suspected of damaging fertility or the unborn child.

ChemSec’s SIN List, a database of chemicals likely to be banned or restricted in a near future, includes cyclomethicone as a

possible reprotoxic chemical (R3) and is categorized as an endocrine disruptor (cat 1). It is a potential PBT/ vPvB substance* and has been detected in various environmental samples including biota and humans.

*PBT and vPvB substances stand for

  • Persistent – chemicals that do not break down in the environment.
  • Bioaccumulation – substances that build up in organisms.
  • Toxicity – harming the entire food chain, animals as well as humans, with effects like cancer, endocrine disruption, and reproductive problems.

Cyclomethicone uses in cosmetics

Cyclomethicones are a type of liquid silicones used in all kinds of cosmetic products*.

Products with cyclomethicone for the skin has an emollient effect. Which means that it coats, protects and lubricates the skin.

However, since it is a silicone, there are anecdotal evidence for that it clogs the skin and causes acne. Which is why cyclomethicone in skin-care often is avoided those that are prone to breakouts.

The emollient effect is by many experts also considered to be temporary. It might in fact make the skin drier as it is not adding any real moisture, it is more like a coated layer on top of the skin.

Cyclomethicone in hair products works in a similar way, where it, for instance, makes the hair less static.

Other products where it is found, and also used to leave a non-stick surface, is for example deodorants.

We use the European Commissions definition of Cosmetics:
“Cosmetics range from everyday hygiene products such as soap, shampoo, deodorant, and toothpaste to luxury beauty items including perfumes and makeup”.

Did you find this ingredient in a product?

Comment and share with a link!