Ceramide AS

What it is

Ceramides are the most abundant fat in the stratum corneum, the outermost layer of skin, where they stack with cholesterol and free fatty acids into the lamellar sheets that hold water in and keep irritants out. The letters in a ceramide's INCI name are a specification of its two halves rather than a grade. The first letter gives the fatty acid - N for a normal, non-hydroxy acid, A for an alpha-hydroxy acid, EO for an omega-hydroxy acid that carries a second fatty acid esterified on its far end. The second letter gives the sphingoid base - S for sphingosine, P for phytosphingosine, G for sphinganine. Ceramide AS is an alpha-hydroxy fatty acid joined to sphingosine. Two retired names collapsed into this one in 2014: Ceramide 4 and Ceramide 5, which differed only in that the acylating hydroxy acids were generally shorter in Ceramide 4 than in Ceramide 5. The single modern name therefore covers a slightly wider range of chain lengths than either of the old ones did, and a pack may still print either.

How it shows up on a label

What it does well

• Restores a lipid the skin makes itself

  Ceramide AS belongs to a subclass of ceramide found naturally in the stratum corneum, so it tops up a lipid the skin already produces. The Panel that assessed these ingredients commented that they would not be readily absorbed through the skin and are expected to remain in the stratum corneum. That is where the effect sits, and it is also the limit of it.

  Moderate evidence

• Works as part of a lipid mixture rather than alone

  Barrier research found that applying one or two of the three physiological lipids - ceramides, cholesterol and free fatty acids - actually delays barrier recovery, and that only complete mixtures allow normal repair. A list carrying ceramides alongside cholesterol and a fatty acid is following that evidence, which is a reason to read the surrounding rows rather than the ceramide line on its own.

  Strong evidence

Worth knowing

• Present at low levels

  The highest maximum concentration reported to the CIR survey for products left on the skin was 0.2%, in skin care preparations. Suppliers separately reported ceramide 5, one of the two materials this name replaced, used at up to 2% in cosmetic products, with no further detail given. Ceramides are expensive raw materials, so a product may advertise them and still contain a fraction of a per cent.

  Matters most toAnyone paying a premium specifically for ceramide content.

• One subclass is not a barrier score

  The familiar line that ceramides are depleted in eczema describes the overall profile, and the picture per subclass is more complicated than that. In an observational study of 213 children with atopic dermatitis, two of the twelve subclasses measured - the AS and NS types - were higher than in controls and tracked with severity. Reading any single ceramide on a label as a measure of barrier health is therefore a mistake, whichever letters it carries.

  Matters most toAnyone choosing a mask by counting the ceramides on the list.

Where the EU stands

Sources (3)

Every link goes to the original: a journal, a PubMed record or an EU document.

1. [1]
   Safety Assessment of Ceramides as Used in Cosmetics

   Cosmetic Ingredient Review Expert Panel · 2015

   The Panel concluded that the ceramide ingredients, including this one, are safe in cosmetics in the present practices of use and concentration described in the assessment, and recorded that they are not restricted in any way under the rules governing cosmetic products in the European Union.

2. [2]
   Optimization of physiological lipid mixtures for barrier repair

   Journal of Investigative Dermatology · 1996 · doi:10.1111/1523-1747.ep12340135

   Ceramides, cholesterol and free fatty acids must be applied together for normal barrier recovery, and increasing any one of the three up to threefold accelerates repair further.

3. [3]
   Skin Ceramide Profile in Children With Atopic Dermatitis

   Dermatitis · 2018 · doi:10.1097/DER.0000000000000392

   In 213 children, two of the twelve ceramide subclasses measured - the AS and NS types - were higher than in controls and tracked with disease severity, so a single subclass does not read as a barrier score.