Seawater has a long history of use in treating various skin conditions, including dermatitis, with origins in the tradition of "balneotherapy" (therapeutic bathing). In recent years, some scientific studies have explored the potential benefits of seawater and its minerals (such as magnesium, calcium, and potassium) for inflammatory skin conditions. Several small-scale studies and clinical observations suggest that bathing in mineral-rich seawater or similar solutions (like those found in the Dead Sea) can help reduce inflammation, itching, and scaling associated with dermatitis, particularly atopic dermatitis and psoriasis. The proposed mechanisms include improved skin barrier function, anti-inflammatory effects, and enhanced hydration due to the osmotic properties of the minerals.

However, the scientific evidence is limited in quality and quantity. Most studies are small, lack rigorous controls, or use mineral-rich solutions rather than direct seawater. There is a lack of large-scale, high-quality randomized controlled trials specifically evaluating ordinary seawater for dermatitis. Some dermatologists caution that seawater can also be irritating or drying to some individuals, especially if the skin is broken, and may carry a risk of secondary infection if the seawater is not clean.

In summary, while there is some preliminary scientific support for the use of mineral-rich water, including seawater, in managing dermatitis symptoms, the overall evidence is modest (rated 2/5). It is best considered an adjunct to standard therapies rather than a primary treatment.