How does the gut microbiome influence eczema?

The gut microbiome is involved in the regulation of immune function, with symbiotic bacteria helping to curtail immune activation that can aggravate atopic dermatitis. There is evidence that the gut microbiome is less diverse and there are fewer of some beneficial species in people with atopic dermatitis.^[1] Interestingly, dysbiosis in infants is associated with atopic dermatitis later in life.

It’s possible that, instead of alterations in the skin microbiome causing atopic dermatitis, the skin condition leads to microbial changes. Consequently, these changes in the skin microbiome can be seen as more of an exacerbating factor in atopic dermatitis rather than an initial cause, though a causal role is possible in some instances.^[2][3] In atopic dermatitis, the lesions are extremely likely to have an overabundance of the bacterium Staphylococcus. aureus, which can worsen inflammation and lead to dysregulated desquamation and insufficient beneficial species. Fungi of the Malassezia genus, as well as some others, may also aggravate atopic dermatitis in some scenarios. There is also the phenomenon of the herpes simplex virus migrating to atopic dermatitis lesions and causing complications, called eczema herpeticum.^[3]

Lower microbial diversity and low populations of beneficial species in the gut are associated with the risk for atopic dermatitis. When it comes to the skin microbiome, an imbalance is likely more of a consequence of atopic dermatitis than an initial cause, though a partial role can’t be ruled out in some cases.