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

References

	Smit LAM, Heederik D, Doekes G, Blom C, van Zweden I, Wouters IM, Exposure–response analysis of allergy and respiratory symptoms in endotoxin-exposed adults, Eur Respir J, 2008;31:1241-1248,

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