Eczema, formally known as atopic dermatitis, is a prevalent inflammatory skin condition that causes dryness, intense itching, and visible inflammation. Many people assume that drinking more water will resolve the problem by sending extra fluid directly to the skin’s surface. The central question is determining the true scientific relationship between the body’s internal fluid balance and the hydration of the outermost layer of the skin.
Understanding Eczema and Barrier Function
Eczema is rooted in inflammation and a structural defect in the skin’s outer protective layer, the stratum corneum. This layer acts like a wall, composed of dead skin cells held together by a lipid matrix of ceramides and fatty acids. In eczema patients, this barrier is often genetically compromised due to mutations in proteins like filaggrin, which maintain the skin’s structure.
The dryness associated with eczema is not merely dehydration but a failure of the skin to retain moisture. This failure is measured by transepidermal water loss (TEWL), the passive evaporation of water vapor through the skin. When the skin barrier is damaged, TEWL increases significantly, causing the skin to rapidly lose water and become dry and irritated.
Systemic Hydration and Skin Moisture Levels
The idea that drinking large amounts of water directly hydrates the superficial layer of the skin lacks scientific support. The fluid consumed primarily hydrates the deeper skin layers (dermis and epidermis) and is distributed throughout the body before reaching the surface. The stratum corneum receives hydration via diffusion from the dermis, but this process is highly regulated and limited by the skin’s barrier properties.
For clinically dehydrated people, increasing fluid intake can slightly improve skin elasticity and hydration. However, for individuals who already drink the recommended daily amount, consuming more does not significantly increase the water content of the outermost stratum corneum. The skin is designed as a barrier, preventing internal water from escaping and limiting how much water reaches the surface.
Studies show that while increased water intake may slightly improve overall skin hydration, applying a moisturizer has a far more favorable and immediate impact on the stratum corneum. Systemic hydration is necessary for overall health, but it cannot fix the fundamental barrier defect causing excessive water loss. Adequate water intake is a supportive measure, not a direct treatment for eczema-related dryness.
Topical Water Application and Sealing the Barrier
Since increasing internal fluid intake does not solve water loss, the most effective use of water for eczema management is external application followed by immediate occlusion. This is the foundation of the “soak-and-seal” method, designed to physically introduce water into the compromised outer skin layer. The process involves soaking the skin in lukewarm water for five to ten minutes, allowing the outer cells to absorb the moisture.
After soaking, the skin should be gently patted dry, leaving some dampness on the surface. Within a three-minute window, a thick occlusive moisturizer or ointment must be applied liberally over the affected area. This immediate application creates a physical seal that traps the absorbed water, preventing the rapid transepidermal water loss that bypasses the skin’s defective barrier function.
This method successfully rehydrates dry skin and improves flexibility, reducing flaking and cracking during a flare. By introducing water directly and sealing it in, the soak-and-seal technique temporarily restores the moisture balance that eczematous skin cannot maintain. Regular practice of this regimen is a primary tool for managing dryness and reducing flare-up severity.
How Water Quality Impacts Eczema
The quality of the water itself can influence eczema symptoms. Hard water, which has a high concentration of dissolved minerals like calcium and magnesium, is a common environmental irritant. These minerals react with soaps and cleansers, forming a residue that remains on the skin.
This residue disrupts the delicate skin barrier, and the minerals elevate the skin’s pH level, making it more alkaline. A higher pH interferes with the function of the skin’s natural enzymes, further compromising the barrier and increasing susceptibility to irritation and bacteria. Studies show an association between living in hard water areas and an increased risk of developing eczema in infants.
Chlorine, often added to tap water as a disinfectant, can strip the skin of its natural oils, leading to dryness and irritation. For those who suspect water quality is a trigger, practical steps can mitigate the effects. Installing a whole-house water softener or using a showerhead filter to reduce chlorine content may help decrease irritation and support skin recovery.