House Dust Endotoxin and Allergic
Sensitization in Children
Gehring U, Bischof W, Fahlbusch B, Wichmann HE, Heinrich J
American Journal of Respiratory and Critical Care Medicine
Several studies have linked endotoxins, components of the
outer membrane of Gram-negative bacteria, to strong proinflammatory immune
The data defining the role of endotoxins in
asthma have, however, presented conflicting views. While some studies suggest
that endotoxins trigger asthmatic responses by inducing an airway inflammation,
others seem to indicate that endotoxin exposure activates type-1 T-helper cell
responses, thus having a protective effect on atopy.
study examined the association between house dust endotoxin and allergic
sensitization in children growing up on a farm.
Seven hundred forty children, aged 5 to 10 years, were
screened via a 78-item cross-sectional survey, and data from 444 children were
selected for inclusion in this study. Of the children selected for inclusion,
50% were atopic or had physician-diagnosed asthma. All of the children included
in this data set completed IgE testing for house dust mite Dermatophagoides
(d1), cat dander (e1), grass pollen (g6), birch pollen (t3),
and Cladosporium herbarum
(m2). In addition, dust samples collected by
vacuuming the living room floors in their homes were taken and analyzed for the
presence of endotoxins.
The endotoxin levels collected from the living room floors
ranged from 160 to 2,670,001 EU/m2
, with geometric mean of 24,221
. Overall, 23% of the children's parents were found to be
atopic, and 22% of the families lived with an indoor dog and/or cat. The data
revealed a negative association between exposure to endotoxins and a
sensitization to 1 or more allergens (aOR [95% CI] 0.95 [0.83; 1.10]) and 2 or
more allergens (aOR [95% CI] 0.80 [0.67; 0.97]). Children who had lived in the
same home since birth were found to have a stronger protective effect by
endotoxin exposure on sensitization to indoor allergens than children who had
moved to a new home at least once during their lifetime.
Based on these data, the researchers concluded that exposure
to higher levels of house dust endotoxin has a protective effect and is
associated with lower prevalence of allergic sensitization in children.
J, Pearce N, Heederik D. Does environmental endotoxin exposure prevent
asthma? Thorax. 2002;57:86-90.
O, Kips J, Duchateau J, et al. Severity of asthma is related to endotoxin
in house dust. Am J Respir Crit Care Med. 1996;154:1641-1646.
O, Duchateau J, Sergysels R. Effect of inhaled endotoxin on bronchial
reactivity in asthmatic and normal subjects. J Appl Physiol.
JE, Leung DYM, Thatayatikom A, et al. Relation between house-dust
endotoxin exposure, type 1 T-cell development, and allergen sensitization
in infants at high risk of asthma. Lancet. 2000;355:1680-1683.
For more information, contact:
Alan L. Wozniak, CIAQP
(800) 422-7873 ext. 802