Endotoxin exposure reduces hayfever but increases respiratory symptoms in adults
The study found that current occupational exposure to
endotoxin was associated with a reduced prevalence of hay
fever in adults, regardless of childhood exposure. However, in
the same population, a positive dose-dependent association
between endotoxin exposure and adverse respiratory effects,
such as wheezing, shortness of breath and cough, was found.
The possible confounding effects of biocides was eliminated by confining the farming population to organic farmers and controlling for childhood farm exposure.
The pro-inflammatory properties of endotoxin can explain the
increased risk of airway symptoms such as wheezing and
cough. Conversely, endotoxin is thought to reduce the risk of
allergic sensitisation by inducing a shift from allergic T-helper
cell (Th) type 2 responses to Th1-dominated responses,
through stimulation of the innate immune system and
regulatory T-cells. The results of the present study suggest
that inhaled endotoxin may exert such immune-modulating
effects beyond childhood, and similar conclusions were
previously derived from a longitudinal study showing that
young adult dairy farmers may lose allergic sensitisation over
time, especially to grass pollen
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