Ceramides

Ceramides make up roughly 40% to 50% of the fats between cells in the skin's outer layer, where they help control water loss and keep irritants out. Dry, irritated and ageing skin tends to have lower levels [2]. The letters on labels describe the molecule: Ceramide NP was once called Ceramide 3, Ceramide AP was Ceramide 6 II and Ceramide EOP was Ceramide 1 [1]. Cosmetic ceramides are almost all made in labs [2].

You'll often see claims about a 3:1:1 ratio of ceramides, cholesterol and fatty acids. That idea comes mainly from mouse barrier-repair studies, where an optimal ceramide-dominant mix sped recovery and incomplete mixes could slow it [3]. The reviewing author co-developed a ceramide-dominant prescription product, and brands rarely disclose ratios, so you can't check this on a label.

In people, the evidence is for whole moisturisers. A 2023 meta-analysis of five studies found ceramide moisturisers gave a small, statistically significant improvement in eczema severity scores compared with other moisturisers (two studies), but no significant difference in water loss [4]. A second meta-analysis that pooled three tiny studies (32 people) also found no significant difference in water loss [5].

Individual trials, mostly small and often linked to brands, report bigger effects: one in 107 children found a ceramide cream reduced eczema severity more than a glycerol cream, and one in 121 children found a ceramide-dominant cream performed similarly to a mild steroid cream over 28 days [6]. In healthy adults with dry skin, a ceramide lotion funded by its maker raised hydration within 24 hours, but it also contained glycerin, hyaluronic acid and shea butter [7].

Ceramides are low-percentage ingredients, typically up to about 0.2% in face products [1], which is why the whole formula matters more than the word 'ceramide' on the front of the pack. Patch tests in 33 to 44 people found no irritation, and a US safety panel judged them safe as used in cosmetics [1].