Castile soap, a vegetable oil-based soap (typically olive oil), has a long history of use for general skin cleansing and is traditionally regarded as a gentler alternative to harsher soaps or detergents. For eczema, its use is primarily supported by anecdotal and traditional beliefs rather than robust scientific evidence. Historically, Castile soap has been recommended because it lacks synthetic fragrances, dyes, and harsh surfactants that can irritate sensitive or eczematous skin. However, there are no well-controlled clinical trials or scientific studies directly validating its efficacy or safety specifically for eczema treatment or management.

Dermatologists often suggest gentle, fragrance-free cleansers for individuals with eczema to minimize irritation and preserve the skin barrier. While Castile soap fits these criteria, it can still be drying for some people, as all soaps have a basic pH and can remove skin oils. Most recommendations for Castile soap in eczema are therefore based on its traditional reputation for mildness and the absence of certain irritants, not on scientific validation. People with eczema are generally advised to patch test any cleanser and to use moisturizers immediately after washing to help restore skin hydration.

In summary, Castile soap’s use for eczema is justified by tradition and its ingredient profile, not by direct scientific proof of benefit.