Skin dryness and scaliness is very common in winter. Skin is a living organ that changes with our surroundings but winter tests its resilience with drops in temperature, more wind, less sunlight, more indoor living, more central heating, and often changes in our diet.
Skin has three layers, the uppermost epidermis, containing scaly structural keratinocytes, immune cells, enzymes, and important lipids and molecules that create our waterproofing lipid bilayer; the dermis in the middle, housing blood vessels, nerves, immune cells, water-loving glycosaminoglycans, and providing strength and stretchiness through collagen and elastin; and the subcutaneous fat layer, which cushions us, provides energy and interacts with other body systems.
The Importance of the Epidermis
Keratinocytes, the lipid bilayer and supporting molecules in the epidermis form our skin barrier, which stops the water in our body from evaporating, protects us from infection and limits damage from UV radiation. The skin barrier is a bit like a brick wall. Intact brick walls are brilliant barriers, but crumbling, leaky walls provide less protection. The levels of water, lipids and supporting molecules in the epidermis determine whether our skin barrier functions well or not. There is a drop in the volume of lipids in the epidermis in winter, less water in the epidermis at colder temperatures, and wind encourages water loss across the epidermis by reducing humidity at the skin surface 1,2 . Central heating warms and dries indoor air, but dry air encourages water to move out from our epidermis into the atmosphere, and a leaky skin barrier allows this to happen more easily. We spend around 60-80% of our day indoors 3 , so exposure to dry air here can really affect our skin.
Everyday, water-dependent enzymes at our skin surface are at work breaking bonds between old keratinocytes so that these cells can be lost in a process called desquamation. If there is less water, desquamation reduces and cells build up. Scaly skin looks dull and feels rough, as the bunched up cells do not reflect light as well as a smooth surface.
Countering the Climate
Moisturisers help maintain and repair the skin barrier. Active ingredients can have occlusive, emollient and/or humectant actions. Occlusives like petrolatum and liquid paraffin provide a waterproof coating over the skin. Emollient oils and lipids fill in gaps between craggy keratinocytes and smoothen the skin, and humectants like glycerin attract water from the atmosphere and other skin layers. Used together these ingredients protect and improve dry skin.
Harsh surfactants in washes can remove elements of the skin barrier, leading to skin drying further. Look for gentle synthetic washes and avoid true soaps. Foaming is often thought necessary for cleansing, but this isn’t actually the case, and very foamy washes often contain the harshest surfactants. As well as moisturisers working to retain water in the skin, physical exfoliation with body scrubs or chemicals (alpha-hydroxy acids [AHAs] like lactic and glycolic acids, and beta-hydroxy acids [BHAs] like salicylic acid) can encourage desquamation, reducing scaliness.
In summary, changes in the weather and in the lifestyles we lead in winter put strain on our skin barrier, leading to loss of water, lipids and important molecules from our skin. Avoiding long periods in dry air, using gentle washes, a daily moisturiser, and appropriate exfoliation can improve skin’s health, appearance and texture.
1. Engebretsen KA, Johansen JD, Kezic S, Linneberg A, Thyssen JP. The effect of environmental humidity and temperature on skin barrier function and dermatitis. J Eur Acad Dermatol Venereol. 2016;30(2):223-249 2. Bolton N. Why does humidity and wind speed affect evaporation? [Internet]. United States: Sciencing.com; [updated 2018 March; cited 2019 June]. Available from: https://www.sciencing.com/humidity-wind-speed-affect-evaporation-12017079.html 3. Jantunen M, Oliveira Fernandes E, Carrer P, Kephalopoulos S. Promoting actions for healthy indoor air (IAIAQ). European Commision Directorate General for Health and Consumers. 2011. Available online at : http://www.iaquk.org.uk/ESW/files/env_iaiaq.pdf