The skin’s barrier function depends on it maintaining optimum moisture levels.

It continuously protects the body from noxious stimuli, e.g., microorganisms, ultraviolet (UV) irradiation, allergens, and irritants. Its unique role and function is a direct result of its structure and makeup, particularly of the most superficial part, the epidermis.
The superficial layer of the skin, the stratum corneum, is like a brick wall in which the corneocytes are the “bricks” surrounded by the intercellular lipid lamellae that act like the “mortar” to maintain both skin’s integrity and permeability barrier.⁽¹⁾

The skin’s barrier function depends mainly on the integrity of the stratum corneum. Skin dryness happens when hydration of the stratum corneum decreases and transepidermal water loss increases (TEWL).

Additionally, dry skin (with or without clinical desquamation) is often associated to reduced barrier function and sensitive skin.
Redness, itching, stinging, tightness and just an uncomfortable feel are not unusual to both these skin conditions.
If the skin can't keep moisture in, it becomes easily irritated, weak and unhealthy in appearance.
Dry skin is an uncomfortable condition marked by scaling, itching, and cracking and may occur for a variety of reasons.⁽²⁾

Aging makes skin more susceptible to dryness.

There are various potential etiologies of dry skin in older people including reduced epidermal differentiation and lipid synthesis.

Some body areas not covered by clothes can be more susceptible to dryness such as the hands and the face especially during winter time due to environmental factors.⁽³⁾

Dry skin can affect any part of the body, but it commonly affects hands, arms, and legs. Dry skin occurs gradually and follows a progressive worsening:

• > Dry skin feels tight and may appear slightly to moderately rough. Dry skin may be present in conditions such as atopic dermatitis, psoriasis and eczema.
• > Very dry skin can be very tight, very rough and itchy and may also start to appear scaly and flaky.
• > Extremely dry skin feels extremely rough, scaly and flaky and may also be severely itchy. In extreme cases skin might also crack. This phenomenon is particularly common in areas that need to flex during movement such as the soles of the feet.

At a molecular level, changes in skin lipids, filaggrin and Natural Moisturising Factor (NMF) can play an important role in the generation of dry skin.

Dry skin management typically involves application of emollients and optimized lipid mixtures.

It has been previously recommended that an ideal emollient contains five key components: humectants, non-physiological lipids (e.g. mineral, vegetable oil), physiological lipids (e.g. ceramides, free fatty acids), antipruritics/soothing agents, and agents that support epidermal differentiation.^(3),(4),(5)

Urea is an organic compound that has been used clinically for dermatological diseases for more than a century. Urea is a potent emollient and keratolytic agent, making urea an effective monotherapy for conditions associated with dry and scaly skin.⁽⁶⁾

Urea plays a significant role in moisture regulation and is a key constituent of NMF the chemical protective coat produced by the epidermis and responsible for keeping the adequate hydration of stratum corneum- the outermost part of the epidermis.

The NMF consists primarily of amino acids (~40%) and their derivatives, including pyrrolidone carboxylic acid (PCA, ~12%), lactate (~12%), urea (~7%), and inorganic salts (~18%).⁽⁷⁾

To help heal dry skin dermatologists recommend to:

• > Apply moisturisers immediately after washing
• > Use only gentle, unscented skin care products with no alcohol, fragrance, retinoids, or acids
• > Avoid irritating clothes and hypoallergenic laundry detergents

^{(1) The structure and function of the stratum corneum. Menon GK1, Cleary GW, Lane ME.}

^{(2) The Prevalence of Sensitive Skin Miranda A. Farage}

^{(3) Proksch E, Lachapelle JM. The management of dry skin with topical emollients: recent perspectives. J Dtsch Dermatol Ges 2005; 3(10):768-74}

^{(4) Emollient therapy for dry and inflammatory skin conditions. Green, L. (2011). Nursing Standard, 26(1),39–46. https://doi.org/10.7748/ns2011.09.26.1.39.c8692}

^{(5) Filaggrin mutations increase the risk for persistent dry skin and eczema independent of sensitization. Böhme, M., Söderhäll, C., Kull, I., Bergström, A., van Hage, M., & Wahlgren, C.-F. (2012). Journal of Allergy and Clinical Immunology, 129(4), 1153–1155. https://doi.org/10.1016/j.jaci.2011.11.032}

^{(6) Urea: a comprehensive review of the clinical literature. Pan M1, Heinecke G, Bernardo S, Tsui C, Levitt J.}

^{(7) Treatment of Xerosis with a Topical Formulation Containing Glyceryl Glucoside, Natural Moisturizing Factors, and Ceramide Teresa M. Weber, PhD,a Martina Kausch, Dipl Eng,b Frank Rippke, MD,b Andrea M. Schoelermann, MD,b and Alexander W. Filbry, PhDb}