Propionibacterium freudenreichii is a probiotic bacterium traditionally used in the fermentation of Swiss-type cheeses. In recent years, some scientific research has investigated its potential benefits for immune modulation and skin health, including its role in atopic dermatitis (eczema). Several small-scale human clinical trials and animal studies suggest that supplementation with P. freudenreichii (often in combination with other probiotics) may help modulate immune responses, reduce inflammation, and improve skin barrier function. For example, a randomized controlled trial published in 2017 found that a mixture containing P. freudenreichii reduced eczema severity in infants at high risk of atopic disease (Niers et al., 2009). Animal studies have also shown reductions in skin inflammation and improvement in symptoms with supplementation.

The mechanisms appear to involve modulation of gut microbiota, production of beneficial metabolites (such as short-chain fatty acids), and regulation of immune responses (e.g., balancing Th1/Th2 cytokines). However, direct evidence for P. freudenreichii alone (not as part of a probiotic mixture) is limited, and most studies are preliminary, with small sample sizes and varying methodologies. Thus, while there is some scientific evidence supporting its use for eczema, it is not robust, and larger, well-controlled studies are needed. The current evidence base justifies a modest rating of 2 out of 5.