Dysregulation of the human microbiome has been a common clinical feature observed in patients with atopic dermatitis (AD) and food allergy (FA).¹ Since diet can lead to fluctuations in the microbiome, dietary modifications may serve as modulators for skin microbial composition.¹ In mouse models, diets low in fatty acids have been associated with impairment in epithelial barrier functions.¹ In addition, patients with both AD and FA have more severe epithelial barrier function impairment than those with AD only, further suggesting that dietary fat is essential for skin barrier function.¹ Nevertheless, studies that investigated the efficacy of dietary modifications in the management of AD has been limited due to inconsistent outcomes and an incomplete understanding of the complex interactions behind the skin and gut microbiomes.¹ During the 2024 AAAAI Annual Meeting, Dr. John Fyolek from Northwestern University Feinberg School of Medicine, the United States, shared the results of a study examining the effect of high-fat diets on skin microbiome in children with food allergies and eczema.

A total of 113 patients aged ≤13 years with FA in the large, prospective, multicenter cohort study, FORWARD, were included.¹ A total of 90 patients were diagnosed with AD.¹ Skin samples from retro-auricular creases and antecubital fossa were collected and subjected to metagenomic sequencing.¹ Dietary assessments with the Automated Self-Administered 24-hour Dietary Assessment Tool (ASA24) were also performed concurrently.¹

The study found that high dietary fat intake (≥35% total kilocalorie intake) was associated with 46 and 80 unique differentially abundant (DA) bacteria species in FA patients with and without comorbid AD respectively (false discovery rate<0.05).¹ High dietary fat intake was also associated with a reduced abundance of potentially pathogenic bacteria (e.g. Staphylococcal aureus) among patients with comorbid eczema and an increased abundance of commensal bacteria (e.g. Staphylococcal epidermis) among patients without eczema compared to their low-fat intake counterparts.¹ However, dietary fat intake did not influence alpha or beta microbiome diversity indices in FA patients.¹

In conclusion, dietary fat intake may play a role in the regulation of the epithelial barrier function.¹ Low-fat diet may contribute to impairments of epithelial barrier function and produce a more favorable environment for pathogenic bacteria, resulting in the exacerbation of eczema.¹ Further investigations and assessments are necessary to validate this correlation.¹