Urea is also produced naturally by the skin and is part of the essential Natural Moisturizing Factor (NMF) which regulates skin’s moisture content. Urea is hygroscopic, which means it is able to bind moisture into the outermost layer of skin, thus relieves itching and roughness, helping  to  fight  dry  skin symptoms. It is also keratolytic, meaning it improves natural exfoliation and soothes and smoothes the skin’s surface. As a substance produced naturally by the skin, Urea is well-tolerated even by dry and sensitive skin. Because all of these effects and very good study data, Urea is the gold standard in treating of dry skin.*

* Reference: Augustin M et al., diagnosis and treatment of xerosis cutis – a position paper, JDDG 2019, DOI: 10.1111/ddg.13906

Ceramides are important lipids in the hydrolipid film (which protects the external layers of skin). Produced naturally in healthy skin, they strengthen the skin barrier, helping to prevent moisture loss due to evaporation and keeping out irritants that can cause inflammation and itching. When skin’s Ceramide levels fall the skin barrier is impaired. Skin can start to lose water and become dry and irritated.
Eucerin uses synthetic Ceramides that are biologically-identical and that enhance skin’s natural barrier – locking in moisture and preventing dryness and irritation. ;

NMFs are a variety of water soluable compounds like amino acids, Urea and Lactic Acid which naturally occur in the stratum corneum (outer layer of the epidermis). They increase the water-binding capacity of the skin, keeping it well hydrated.