Ceramide AP

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 AP is an alpha-hydroxy fatty acid joined to phytosphingosine. It was formerly called Ceramide 6 II, a name retired in 2014, and packs may still print either. The extra hydroxyl group on the fatty acid gives it more scope for hydrogen bonding than a plain N-type ceramide has, which is measurable in models of the barrier.

How it shows up on a label

What it does well

• Behaves differently from the sphingosine ceramides

  In a hydrated model of the skin lipid barrier - each ceramide mixed in equal molar amounts with cholesterol and deuterated stearic acid - infrared spectroscopy found that the phytosphingosine ceramides NP and AP behaved fundamentally differently from the analogous sphingosine systems, and that both raised the temperature at which the fatty acid chains lose their order. This is a physical-chemistry result in a model rather than a clinical one, and it does not show that one letter works better on skin. What it does show is that a list naming several letters is not simply repeating itself.

  Limited evidence

• Restores a lipid the skin makes itself

  Ceramide AP 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

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. That figure names this ingredient directly. Ceramides are among the more expensive cosmetic raw materials, so a product may advertise them and still contain a fraction of a per cent. Where the name falls on the ingredient list is a rough guide to how much is really there.

  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 (4)

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]
   FTIR spectroscopic studies of lipid dynamics in phytosphingosine ceramide models of the stratum corneum lipid matrix

   Chemistry and Physics of Lipids · 2005 · doi:10.1016/j.chemphyslip.2004.12.002

   In a hydrated model of the barrier, the phytosphingosine-based ceramides NP and AP behaved fundamentally differently from the analogous sphingosine-based systems, so the letters mark a real physical difference rather than a naming convention.

3. [3]
   Effects of sphingolipid extracts on the morphological structure and lipid profile in an in vitro model of canine skin

   The Veterinary Journal · 2016 · doi:10.1016/j.tvjl.2016.03.020

   Supplementing a cultured skin model with sphingolipid extract raised several ceramide subclasses, including AP, EOP, NS and AS, showing the subclasses respond as a group rather than singly.

4. [4]
   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.