Ceramide Types Explained: NP, AP, EOP, NS, AS and the Rest

Published: September 2025 · Reading time: approx. 8 minutes

TL;DR - Quick Summary

Ceramides are sphingolipids that form approximately 50% of the lipid matrix of the stratum corneum. There are at least nine structurally distinct types in human skin.
The INCI naming system uses letter codes: the first letter(s) indicate the fatty acid type (N, A, EO), the last letter indicates the sphingoid base (P, S, H). Understanding the code tells you the ceramide's structural position in the lamellar bilayer.
Ceramide NP is the most abundant type and the most common in skincare. But it occupies only one structural position - a product needs multiple ceramide types to restore the full lamellar architecture.
Ceramide synthesis requires linoleic acid (for EOP/EOS types) and phytosphingosine precursors. Products that supply these precursors alongside ceramides support both direct barrier repair and ongoing ceramide production.
Antioxidants - vitamins C and E, resveratrol - protect ceramides from lipid peroxidation and are important companions in any ceramide-containing formulation.

Ceramides appear on more skincare product labels than ever. But the term covers a family of nine structurally distinct molecules, each with a different role in the skin barrier - and most ceramide marketing treats them as interchangeable. They are not. Knowing the difference between ceramide types is the difference between understanding what a product can actually do and accepting a marketing claim on faith.

What ceramides are

Ceramides are a class of lipid molecules called sphingolipids. Structurally, each ceramide consists of a sphingoid base (an amino alcohol backbone) linked via an amide bond to a long-chain fatty acid. This combination creates a molecule that is both hydrophobic and capable of hydrogen bonding - properties that are critical for how ceramides self-assemble into the lamellar bilayer structure of the stratum corneum.

Ceramides make up approximately 50% of the total lipids in the stratum corneum, alongside cholesterol (~25%) and free fatty acids (~25%). These three lipid classes together form the lamellar lipid matrix - the structural mortar between the corneocyte bricks that determines barrier permeability, moisture retention and inflammatory threshold.

Because ceramides are natural skin components, topically applied ceramides are recognised and integrated by the skin without immune response. They are genuinely skin-identical, not an approximation.

How the INCI naming system works - and what the letters mean

The INCI naming system for ceramides was revised in the mid-2010s. Products still in circulation may use the old numeric system (Ceramide 1, Ceramide 3 etc.) but all EU-labelled products since the revision use the letter-code system. Understanding the code makes it possible to identify exactly what structural class of ceramide is present.

Each ceramide INCI name is composed of two parts: the fatty acid class and the sphingoid base class.

First letters - fatty acid class N

Non-hydroxy fatty acid. The standard saturated or monounsaturated fatty acid chain. Most abundant in skin ceramides. Example: Ceramide NP.

First letters - fatty acid class A

Alpha-hydroxy fatty acid. Has a hydroxyl group at the alpha position that creates additional hydrogen bonding capacity. Example: Ceramide AP.

First letters - fatty acid class EO

Esterified omega fatty acid. The fatty acid is esterified with linoleic acid at its omega end. Essential for corneocyte envelope formation. Example: Ceramide EOP.

Last letter - sphingoid base P / S / H

P = phytosphingosine. S = sphingosine. H = 6-hydroxy sphingosine. Each base has a different molecular geometry that determines its structural position in the lamellar bilayer.

So Ceramide NP = non-hydroxy fatty acid + phytosphingosine base. Ceramide EOP = esterified omega fatty acid + phytosphingosine base. Ceramide NS = non-hydroxy fatty acid + sphingosine base. And so on. The combination determines both the ceramide's structure and its specific function in the barrier.

All nine ceramide types: what each one does

INCI Name	Legacy name	Structural role and function
Ceramide NP	Ceramide 3	The most abundant ceramide in the stratum corneum by weight. Primary structural ceramide - essential for lamellar bilayer formation. Most studied in clinical research. Most depleted in atopic dermatitis and reactive skin. The ceramide referenced in most "ceramide NP" or "ceramide 3" skincare products.
Ceramide NS	Ceramide 2	Non-hydroxy fatty acid + sphingosine base. Contributes to lamellar structure at positions that NP cannot occupy due to its different sphingosine backbone geometry. Important component of the barrier's middle lamellae.
Ceramide AP	Ceramide 6-II	Alpha-hydroxy fatty acid + phytosphingosine. The hydroxyl group creates additional hydrogen bonding within the lamellar stack, supporting bilayer stability under stress - humidity changes, temperature variation, inflammation. Particularly relevant for barrier maintenance in reactive skin.
Ceramide AS	Ceramide 5	Alpha-hydroxy fatty acid + sphingosine. Bridges structural roles that neither AP nor NS alone fulfils. Contributes to the hydrogen bonding network of the lamellar bilayer at positions requiring the sphingosine backbone.
Ceramide EOP	Ceramide 9	Esterified omega fatty acid (with linoleic acid) + phytosphingosine. A long-chain ceramide essential for corneocyte envelope structure and cohesion - the protein-lipid boundary layer of the corneocyte itself. Loss of EOP is directly associated with visible barrier failure: scaling, cohesion loss, increased TEWL. Requires linoleic acid for its synthesis.
Ceramide EOS	Ceramide 1	Esterified omega fatty acid (with linoleic acid) + sphingosine. The original "organisation ceramide" - plays a key role in the spatial organisation of the lamellar bodies within which ceramides are stored before secretion. Its linoleic acid ester linkage connects ceramide function to essential fatty acid metabolism.
Ceramide EOH	Ceramide 4	Esterified omega fatty acid + 6-hydroxy sphingosine. The 6-hydroxy sphingosine base provides an additional hydroxyl interaction point. Found in lower concentrations than the major ceramide classes; contributes to the completeness of the lamellar lipid spectrum.
Ceramide NH	Ceramide 8	Non-hydroxy fatty acid + 6-hydroxy sphingosine. Contributes to lamellar structure with the 6-hydroxy sphingosine base; found predominantly in the upper strata of the stratum corneum.
Ceramide AH	Ceramide 7	Alpha-hydroxy fatty acid + 6-hydroxy sphingosine. The combination of alpha-hydroxy fatty acid and 6-hydroxy sphingosine maximises hydrogen bonding potential; found in smaller quantities but contributes to the upper-layer lamellar integrity.

The five ceramide types NAYA uses - NP, AP, EOP, NS and AS - were selected to address the five primary structural positions in the lamellar bilayer. This is not a quantity decision. It is an architecture decision.

Which skin types and conditions benefit most from ceramides

Because ceramides are natural skin components, every skin type benefits from ceramide-containing formulations when the skin barrier is under stress. The benefit scales with the degree of barrier compromise - the more depleted or disrupted the lamellar lipid matrix, the greater the measurable effect of ceramide supplementation.

Dry and dehydrated skin

Persistent dryness that does not resolve with conventional moisturisers is often a ceramide deficiency problem rather than a water content problem. If the lamellar lipid matrix is structurally incomplete, trans-epidermal water loss remains elevated regardless of how much water or humectant is applied to the surface. Ceramide-containing formulations that restore the lamellar structure address the mechanism, not just the symptom.

Sensitive and reactive skin

Ceramide levels are measurably reduced in sensitive skin and in post-procedural states (over-exfoliation, retinoid adjustment, chemical peel recovery). The depleted lamellar matrix allows irritants to penetrate more readily and sensitises nerve endings - the mechanism behind escalating reactivity that many people experience as their skin becoming "more sensitive over time."

Atopic dermatitis and eczema-prone skin

Research consistently documents ceramide depletion across multiple ceramide types in atopic dermatitis - not just Ceramide NP, but EOP, NS and others simultaneously. This is the clinical evidence base for the argument that multi-ceramide formulations are more structurally appropriate for eczema-prone skin than single-ceramide products.

Ageing skin

Ceramide synthesis decreases measurably from approximately the third decade of life onwards. The progressive decline in both ceramide quantity and ceramide diversity contributes to age-related increases in dryness, sensitivity and barrier vulnerability. Topical ceramide supplementation and formulations that support synthesis are among the most evidence-supported approaches to slowing this aspect of skin ageing.

How the skin produces ceramides - and how skincare can support it

Ceramide synthesis takes place in the living epidermis, primarily in the stratum granulosum and stratum spinosum. It proceeds through two main pathways.

The de novo pathway builds ceramides from scratch using sphingosine (or its precursor serine) and a long-chain fatty acid, assembled by the enzyme ceramide synthase. This pathway produces ceramide that is then packaged into lamellar bodies - membrane vesicles that are secreted into the extracellular space between cornifying skin cells, where the ceramides integrate into the lamellar bilayer.

The sphingomyelin pathway produces ceramides by enzymatic hydrolysis of sphingomyelin - a membrane phospholipid found in the cell membranes of keratinocytes. Phospholipids in the cell membrane serve as a precursor reservoir for ceramide synthesis through this pathway.

Skincare that supplies ceramide precursors rather than only finished ceramides can stimulate ongoing synthesis - meaning the effect continues after the product has been metabolised, rather than relying entirely on direct ceramide deposition.

Key synthesis requirements

Two materials are critical for complete ceramide synthesis that many formulations do not supply:

Linoleic acid (Omega-6) is the essential fatty acid required for the synthesis of EOP and EOS ceramides - the esterified omega ceramide types. The body cannot produce linoleic acid; it must be supplied externally. Linoleic acid is consistently depleted in compromised barrier skin. It is found in high concentrations in plant oils including sunflower, safflower and Cacay oil.

Phytosphingosine is a direct precursor to ceramides with phytosphingosine bases (NP, AP, EOP, EOH). Topically applied phytosphingosine can be taken up by keratinocytes and converted into the corresponding ceramide classes, extending the effect of a ceramide formulation beyond what is directly deposited.

The role of phospholipids and linoleic acid in ceramide formulations

Phosphatidylcholine (PC) - listed on INCI labels as Lecithin, Hydrogenated Lecithin or Hydrogenated Phosphatidylcholine - is the most structurally important phospholipid for ceramide support. It serves three roles simultaneously in barrier repair formulations:

First, as a ceramide synthesis precursor: phosphatidylcholine is a sphingomyelin precursor and the cell membrane lipid that the sphingomyelinase pathway breaks down into ceramide. Supplying PC topically supports the ongoing synthesis of ceramides within the living epidermis.

Second, as a linoleic acid source: phosphatidylcholine from plant sources (particularly sunflower lecithin) is naturally rich in linoleic acid. When applied to skin, PC provides a sustained-release linoleic acid depot that can support EOP and EOS ceramide synthesis over time - longer-lasting than direct linoleic acid application because PC is metabolised gradually.

Third, as a delivery system: the bilayer structure of phospholipid vesicles mirrors the lamellar architecture of the stratum corneum. Ceramides and lipids co-formulated with phospholipids are delivered to the barrier in a lamellar structure that integrates more effectively than ceramides in conventional emulsions.

Why ceramides need antioxidant protection

Ceramides are lipids, and lipids are vulnerable to peroxidation - oxidative damage caused by free radicals. Lipid peroxidation breaks down lamellar lipid structures and reduces their barrier function. The key free radical sources affecting ceramides include UV radiation, air pollution, ozone and reactive oxygen species generated by inflammation.

Antioxidants that protect ceramides and the lipid matrix

Vitamin E (Tocopherol) - lipid-soluble antioxidant that integrates directly into the lipid bilayer and intercepts lipid peroxidation chain reactions. The most directly relevant antioxidant for ceramide protection.
Vitamin C (Ascorbic acid) - water-soluble antioxidant that also regenerates oxidised Vitamin E, extending its protective effect. Additionally shown to support ceramide synthesis in cell studies.
Niacinamide - supports ceramide synthesis via multiple pathways including upregulation of serine palmitoyltransferase (the rate-limiting enzyme in de novo ceramide synthesis). Considered among the most well-evidenced ceramide-stimulating topical actives.
Resveratrol and Astaxanthin - potent membrane-active antioxidants with particular affinity for lipid bilayer structures. Provide additional protection at the lamellar level.

A ceramide-containing formulation without antioxidant protection is analogous to rebuilding a structure without weather protection. The ceramides restore the architecture; antioxidants protect it from the ongoing oxidative environment they will encounter in daily use.

How to evaluate ceramide content on a product label

Not all ceramide-containing products are equal, and the INCI list gives you the information to assess what a product is actually providing at the structural level.

Count the ceramide types. A product listing only Ceramide NP provides one structural position in a multi-position architecture. A product listing five or more ceramide types (NP, AP, EOP, NS, AS) provides far more comprehensive structural coverage. Note that this is not simply a "more is better" argument - it is a structural argument about which molecular positions in the lamellar bilayer are being addressed.

Check for cholesterol and fatty acids. Ceramides in a formula without cholesterol and free fatty acids cannot restore the equimolar lamellar ratio that the orthorhombic phase requires. Look for Cholesterol on the INCI list alongside ceramides, and for linoleic acid-rich ingredients (Sunflower Seed Oil, Lecithin, or Linoleic Acid itself) as fatty acid sources.

Check for ceramide precursors. Phytosphingosine and Niacinamide indicate that the formulation supports synthesis as well as direct ceramide delivery. Phosphatidylcholine (or Lecithin / Hydrogenated Lecithin) indicates phospholipid delivery system integration.

Check for antioxidants. Tocopherol (Vitamin E) and Ascorbic Acid or its derivatives alongside ceramides indicate that the formulation has been designed to protect its ceramide content and support ongoing synthesis.

Frequently asked questions

What are ceramides in skincare?

Ceramides are sphingolipids that form approximately 50% of the lipid matrix of the stratum corneum. There are at least nine structurally distinct types in human skin. They are the primary structural component of the skin barrier, and their depletion is measurably associated with increased dryness, sensitivity, reactivity and the conditions that characterise atopic dermatitis.

What is the difference between ceramide NP, AP and EOP?

Ceramide NP (formerly Ceramide 3) is the most abundant ceramide and the primary structural type. Ceramide AP (formerly Ceramide 6-II) has an alpha-hydroxy fatty acid that creates additional hydrogen bonding, supporting bilayer stability. Ceramide EOP (formerly Ceramide 9) is an esterified omega ceramide essential for corneocyte envelope integrity - it requires linoleic acid for its synthesis and is critical for lamellar organisation.

How do I identify ceramides on an INCI list?

Ceramides are listed as Ceramide NP, AP, EOP, NS, AS, EOS, EOH, NH or AH. The letters encode the structure: first letters indicate the fatty acid type (N = non-hydroxy, A = alpha-hydroxy, EO = esterified omega), last letter indicates the sphingoid base (P = phytosphingosine, S = sphingosine, H = 6-hydroxy sphingosine). Some older products use the numeric system (Ceramide 3, Ceramide 6-II, Ceramide 9 etc).

Why do some ceramide products work better than others?

Because ceramide type and the presence of all three lamellar lipid classes (ceramides, cholesterol and fatty acids in equimolar ratio) matter as much as ceramide concentration. A five-ceramide formula with cholesterol and fatty acids restores the lamellar architecture structurally. A single-ceramide product in a conventional emulsion without cholesterol provides partial benefit. Delivery system also matters: phospholipid-based delivery integrates ceramides more effectively into the existing lamellar layers.

How does the skin produce ceramides?

Via two pathways: de novo synthesis (building ceramides from sphingosine and fatty acids) and the sphingomyelin pathway (enzymatic hydrolysis of membrane phospholipids). Key requirements include linoleic acid for EOP/EOS synthesis and phytosphingosine as a direct precursor. Niacinamide upregulates the rate-limiting enzyme of de novo synthesis. Phosphatidylcholine supports both pathways and provides a sustained linoleic acid source.

NAYA

What Are Ceramides? Types, Differences and How to Read Them on INCI Lists

What ceramides are

How the INCI naming system works - and what the letters mean

All nine ceramide types: what each one does