Kefir, a fermented milk drink rich in probiotics, is used to support eczema primarily due to its impact on gut microbiota and immune modulation. Some scientific studies suggest a link between gut health and skin conditions like eczema (atopic dermatitis). Probiotics, including those present in kefir, may improve the skin barrier function and reduce inflammation by influencing immune responses. A few small clinical trials and animal studies have reported that probiotic supplementation can reduce the severity of eczema symptoms, especially in children, and may help prevent eczema when given early in life. For example, a 2015 review in Clinical and Experimental Allergy found limited but promising evidence that certain probiotic strains might reduce eczema risk or severity. However, direct studies specifically on kefir (not just any probiotic) for eczema are limited. Most research focuses on broader probiotic supplementation, and results are inconsistent regarding efficacy, with some studies showing no benefit.

While the mechanistic rationale and some trial data support a role for probiotics in eczema, robust, large-scale clinical trials specifically using kefir are lacking. Therefore, the evidence for kefir's effectiveness in treating or preventing eczema is suggestive but weak. It is best described as having preliminary scientific support, meriting a low to moderate evidence rating.