As the body's largest organ, skin is the first physiological barrier, protecting us from the external environment (2). Among its many purposes, normally functioning skin retains water content and moisture to maintain a soft and pliable texture (1). However, when this function is impaired, skin can become dry and itchy. These symptoms are the hallmarks of a condition that so many children and adults face today: eczema.
Why Does It Happen?
Unless inherited or caused by some other condition, dry skin is referred to as Xeroderma (1). The epidermis layer - specifically, the Stratum corneum - is responsible for the barrier-like function. For this, two conditions must be maintained: intercellular lipids (fatty substances between cells) and moisturizing factor (which helps with water absorption). If either are malfunctioning or out of balance, dry skin can be the result (2).
A Deeper Look
When dry, skin can feel itchy. The itch sensation is initiated by itch-inducing substances binding to peripheral sensory afferent receptors (2). This gives way for a number of sensory neuron/cellular pathways to occur that ultimately induce itchiness. We recommend reading this article to learn more about the mechanisms of itch in dry skin.
Other findings that may help to explain the abnormalities in skin barrier function are:
- Decreases in ceramides (fatty molecules that play a role in skin moisture retention) in patients with atopic dermatitis (eczema), especially in those with filaggrin abnormalities. Filaggrin is a structural protein with a role in skin moisturization (3).
- Histamine is a itch-inducing substance. Antihistamines are blockers of histamine but are not 100% effective in several dermatological conditions that are marked by dry skin. This suggests that dry skin is an important feature of antihistamine-resistant (histamine-independent) itching (2).
- In dry skin diseases, pruritogens (biological mediators of the itching sensation and scratching urge) are released which further aggravates the condition, thereby creating an "itch-scratch cycle" (2).
So, What Can We Do?
Current treatment recommendations include emollients, steroids, calcineurin inhibitors, and immunosuppressants. Additionally, antihistamines and phototherapy can be used to help manage itching and film dressings may act as a barrier to contamination while also reducing itch (2). However, these options may still be used with limited efficacy with potentially serious side effects (3).
source: (2)
Future Directions
The future for dry skin/eczema patients is promising with an abundance of management techniques and therapies constantly developing. New data continues to emerge which gives scientists and physicians a clearer understanding of these kinds of conditions. Though it is not life threatening, dry skin conditions like eczema can be severely debilitating and it seems that science is taking this very seriously.
Skin barrier abnormalities are important to consider. Underlying mechanisms and key regulator molecules in skin barrier function are being uncovered and revealing knowledge which assists the development of promising therapies. Science is hopeful that the near future will provide an opportunity for personalized care for eczema patients (3).
SOURCES:
(1) Lambert, L. (2021). Dry skin. SA Pharmacist's Assistant, 21(2), 20-21.
(2) Moniaga, C. S., Tominaga, M., & Takamori, K. (2020). Mechanisms and management of itch in dry skin. Acta dermato-venereologica, 100(2), 9-20.
(3) Yang, G., Seok, J. K., Kang, H. C., Cho, Y. Y., Lee, H. S., & Lee, J. Y. (2020). Skin barrier abnormalities and immune dysfunction in atopic dermatitis. International journal of molecular sciences, 21(8), 2867.