Why Eczema Gets Worse in Winter (And What to Do About It)

This article is part of the Nella Vosk Complete Guide to Eczema-Friendly Clothing: Fabrics, Fit & Science for Australian Families, and continues from the overview in preparing your eczema child for winter: the complete guide. This article goes deeper into a single question: what is actually happening in the skin during winter that makes eczema worse, and why does understanding the mechanism change how you should respond?

Most parents notice the pattern before they understand the cause: their child’s eczema is calmer through the warmer months and reliably worse from around May through August. It is tempting to treat this as simply ‘bad luck’ or an unavoidable seasonal reality to endure. In fact, winter eczema flares follow a well-documented physiological mechanism, and understanding that mechanism changes the way you respond to it: not with more product applied reactively once the skin has already broken down, but with specific, proactive changes that address the actual cause.

The skin barrier, specifically the outermost layer called the stratum corneum, functions as a protective seal that keeps water inside the body and irritants, allergens, and microbes outside. In eczema-prone skin, this barrier is structurally different from typical skin: it has gaps in its lipid structure that allow water to escape more readily and allow external substances to penetrate more easily. This process of water escaping through the skin is called transepidermal water loss, commonly abbreviated as TEWL.

Healthy skin has a TEWL rate of roughly 4 to 10 grams of water per square metre per hour. In eczema-affected skin, this rate is elevated, sometimes significantly, even in skin that looks clinically clear. This elevated baseline is why eczema-prone skin is more vulnerable to any condition that increases water loss further, and cold, dry air is one of the most significant of these conditions.

Cold air has a lower capacity to hold water vapour than warm air. This means outdoor humidity drops measurably in winter, even in parts of Australia that do not experience extreme cold. When the air around the skin is drier, the water vapour pressure gradient between the skin’s surface and the surrounding air steepens, and water moves out of the skin more rapidly to equalise that gradient. For skin with an already-compromised barrier, this accelerated water loss pushes hydration below the threshold where the barrier can function effectively, and inflammation, itching, and visible flares follow.

If cold, dry air were the only factor, winter eczema management would be relatively straightforward: increase moisturiser to compensate. In practice, several factors compound simultaneously in winter, and the combined effect is larger than any single factor would produce alone.

Indoor heating reduces humidity further

This is the factor most parents do not anticipate. Heating a room does not just raise its temperature; because warm air can hold more water vapour than cold air at the same absolute moisture content, heating effectively lowers the relative humidity inside the room. A family that closes the windows and turns on the heater to escape the cold, dry outdoor air can end up with indoor air that is drier still. Reverse-cycle air conditioning and forced-air heating systems are particularly efficient at this drying effect.

This means the skin gets no genuine relief from the cold, dry conditions outside: the indoor environment, intended as a refuge from the weather, often presents an equally or more challenging humidity environment for the skin barrier.

Hot water compounds the barrier damage

Cold weather increases the temptation to bathe in hot water, both for comfort and out of an instinct to ‘warm up’ a cold child. Hot water strips the skin’s surface lipids, the same lipids that form part of the barrier structure disrupted in eczema, more aggressively than lukewarm water. A hot bath on a cold evening feels immediately soothing but accelerates the same barrier breakdown that the cold air is already causing, compounding rather than offsetting the seasonal challenge.

Wind exposure accelerates local moisture loss

Wind increases the rate of evaporation from any exposed surface, including skin. Face and hand skin, the areas most commonly exposed to wind in winter, experience a locally accelerated version of the same TEWL mechanism affecting the whole body. This is why winter eczema often flares more visibly on the cheeks and hands than on covered areas of the body.

Reduced ventilation and higher indoor pollutant concentration

Windows and doors stay closed more in winter to conserve heat, which reduces the exchange of indoor air with outdoor air. Indoor air can accumulate higher concentrations of dust, pet dander, and other airborne irritants without this ventilation. For eczema-affected children who are also sensitive to dust mites or other airborne allergens, this can represent an additional, independent winter trigger layered on top of the humidity mechanism.

Some research has explored a link between lower vitamin D status in winter (due to reduced sun exposure) and increased eczema severity. Vitamin D has a role in skin barrier function and immune regulation, and observational studies have found associations between lower vitamin D levels and more severe eczema in some populations. The evidence is not conclusive enough to position vitamin D as a primary driver of winter eczema flares, and the mechanical factors discussed above (humidity, indoor heating, hot water, wind) have stronger and more directly demonstrated effects.

Vitamin D status is still worth discussing with your GP, particularly for breastfed babies who require year-round supplementation regardless of season. See vitamin D and breastfeeding: do you and your baby need supplements? for the full guidance.