Ceramide structure and function

What does a ceramide look like?

A ceramide contains a fatty acid component and a component called a sphingoid base. Skin ceramides are a family of related molecules, not one identical substance repeated throughout the skin. Their fatty acid chains and sphingoid bases differ in length and chemical structure. Examples of those bases include sphingosine, dihydrosphingosine and phytosphingosine.1

Some specialised skin ceramides contain very long fatty acid chains and attached linoleic acid. These molecules can span between membrane layers, helping stabilise the structure. Other ceramides become chemically attached to proteins around the outer skin cells. They provide a scaffold on which free lipids are arranged. Chain length, chemical attachments and placement all matter to how the barrier is built.1

Where do ceramides fit in the skin barrier?

The stratum corneum, the outermost layer of skin, contains dead cells called corneocytes in a bricks and mortar arrangement. The familiar bricks and mortar picture is useful, although your face has not quietly become a building site. The cells provide the solid building blocks, while the organised lipid material between them helps control what passes through.2

Ceramides account for about half of the lipid pool in the stratum corneum, rather than half of the entire skin. They sit alongside cholesterol and free fatty acids. Together, these lipids form lamellae: organised, water repelling layers between cells. A functioning barrier needs the components in suitable proportions and properly arranged, not simply a large quantity of one lipid.1

What do ceramides actually do?

Ceramides help the skin limit water loss and resist the entry of allergens and bacteria. This is a structural job: the lipid layers create a barrier between the body and its surroundings. The surrounding barrier system also has antimicrobial properties and helps counter oxidation caused by free radicals. Those functions belong to the organised barrier, rather than to ceramides working alone.13

Water escaping through the epidermis is called transepidermal water loss, often shortened to TEWL. The barrier also controls the movement of chemicals from outside the body inward. Lipid organisation is one factor controlling that movement. The thickness of the outer layer, the number and size of its cells, and how firmly those cells hold together also affect the path substances must cross.2

How does skin make and maintain ceramides?

As keratinocytes, the main epidermal cells, move towards the surface and mature, their lipid production changes. They produce the specialised ceramides needed for the outer barrier. This maturation also produces the proteins and extracellular lipid structures that allow the barrier to form. Genetic changes and excessive immune activity can disrupt the process, altering both the components and their organisation.1

Skin acidity helps maintain this system. The skin surface normally has a pH of 4.5 to 5.5. Enzymes involved in producing ceramides and free fatty acids work best in an acidic environment. Acidity also limits enzymes that break down the connections between outer skin cells. Together with an intact outer layer, the acidic surface supports the normal skin microbiome and discourages harmful microbes from colonising it.2

What happens when the barrier is disrupted?

Barrier health depends on physical structure, skin chemistry and immune regulation working together. Disruption is associated with conditions including atopic dermatitis and psoriasis. Repeated washing with alkaline soaps can raise skin surface pH and favour the growth of certain bacteria. Supporting the barrier therefore involves more than adding ceramides while repeatedly disturbing the environment that helps maintain them.3

What do ceramides in skincare offer?

Natural ceramides occur in skin; synthetic ceramides are made for use in skincare. Products containing added ceramides can replenish these lipids and help keep skin hydrated. Skin replenishes its natural ceramides more slowly with age. Reduced ceramide levels also occur with eczema and can contribute to dehydrated or itchy skin.4

Common ingredient names include ceramide EOS, ceramide NP and ceramide AP. Check the ingredient list to identify them, because the front of the bottle is where an ingredient gets its publicity department. Ceramides appear in moisturizers, serums, lotions and other skincare formats.4

How should you use a ceramide moisturizer?

Apply a ceramide moisturizer to damp skin within three minutes of showering or washing your face. Ceramides work well with humectants, which attract and bind water; emollients, which form a film and ease dryness; and occlusives, which help retain moisture. Compatible ingredients include glycerin, hyaluronic acid, dimethicone, colloidal oatmeal and shea butter.4