Eczema, also known as atopic dermatitis, has been increasing in recent decades, now affecting up to 30% of children in developed countries. While this condition is not life threatening, it negatively impacts a patient’s quality of life. Recent evidence suggests eczema’s causes are not limited only to the skin and that certain gut bacteria thought to be highly beneficial like Faecalibacterium could be involved. To learn more, researchers examined Faecalibacterium collected from patients with eczema, finding distinct variation in appearance and effects on human immune cells across different strains. They then introduced these bacteria to female mice in the lab, which altered the composition of their gut microbial communities. This led to certain strains being linked to decreased butyric and propionic acid levels—effects often linked to eczema—and increased levels of serum lipopolysaccharides in their offspring. These outcomes were enhanced when the mice were fed a low-fiber diet, ultimately leading to elevated systemic inflammation, skin damage, and hair loss in their pups. These findings suggest Faecalibacterium transmission from mother to offspring may play a key role in eczema development and that strategies encouraging the consumption of more dietary fiber could help ease the burden of this condition.