Exposure to endotoxin or other bacterial components might protect against the development of atopy

TLDR

Growing up on a farm protects against atopy, likely because stable dust and farm animals expose children to abundant endotoxin. The study aimed to quantify environmental endotoxin levels in homes of farmers’ children, children with regular livestock contact, and non‑farm controls. Researchers sampled settled and airborne dust from stables, kitchen floors, and mattresses in 84 farming and nonfarming families in rural Germany and Switzerland, measuring endotoxin by a kinetic Limulus assay. Endotoxin concentrations were highest in stables and also significantly elevated on kitchen floors and mattresses of farming families and livestock‑contact households compared to controls, supporting endotoxin as a protective factor against childhood atopy.

Abstract

Background Several recent studies have shown that growing up on a farm confers significant protection against the development of atopy. These findings point particularly towards the importance of exposure to stable dust and farm animals. It has furthermore been reported that endotoxin, an intrinsic part of the outer membrane of gram negative bacteria, is abundant in environments where livestock and poultry is kept. The aim of this study was therefore to measure the level of environmental endotoxin exposure in homes of farmers' children, children with regular contact to livestock and control children with no contact to farm animals. Methods Eighty‐four farming and nonfarming families were identified in rural areas in Southern Germany and Switzerland. Samples of settled and airborne dust were collected in stables, and of settled dust indoors from kitchen floors and the children's mattresses. Endotoxin concentrations were determined by a kinetic Limulus assay. Results Endotoxin concentrations were highest in stables of farming families, but were also significantly higher indoors in dust from kitchen floors (143 EU/mg vs 39 EU/mg, P < 0.001) and children's mattresses (49479 EU/m 2 vs 9383 EU/m 2 , P < 0.001) as compared to control children from nonfarming families. In addition, endotoxin levels were also significantly higher in mattresses and dust from kitchen floors in households where children had regular contact to farm animals (38.6 EU/mg and 23340 EU/m 2 , respectively) as compared to control subjects. Conclusion We propose that the level of environmental exposure to endotoxin and other bacterial wall components is an important protective determinant for the development of atopic diseases in childhood.