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Something old, something new: indoor endotoxin, allergens and asthma
1Division of Pediatric Allergy & Immunology, National Jewish Medical & Research Center, Denver, CO 80206, USA. liua@njc.org
Paediatric Respiratory Reviews
|February 26, 2004
Summary
Early exposure to endotoxin and allergens can paradoxically reduce asthma risk. While indoor allergens increase asthma severity, early exposure to pets and endotoxin may prevent sensitization and asthma development, supporting the Hygiene Hypothesis.
Area of Science:
- Immunology
- Environmental Health
- Epidemiology
Background:
- Endotoxin and allergen exposure are historically linked to asthma development and severity.
- Recent studies challenge traditional views on how these exposures influence asthma inception.
- Indoor allergens are known triggers for inflammation and disease severity in sensitized asthmatics.
Purpose of the Study:
- To explore the complex and often paradoxical effects of endotoxin and allergen exposure on asthma development and sensitization.
- To investigate whether increased indoor allergen exposure leads to sensitization and asthma.
- To examine the role of early-life exposure to animals and endotoxin in asthma prevalence.
Main Methods:
- Review and synthesis of recent epidemiological and immunological studies on environmental exposures and asthma.
- Analysis of dose-response relationships between allergen exposure (e.g., house dust mites, cats) and sensitization.
- Examination of endotoxin exposure data in relation to asthma prevalence, particularly in early life and occupational settings.
Main Results:
- While house dust mite sensitization generally increases with exposure, cat allergen exposure shows an inverse relationship, with higher exposure linked to less sensitization.
- Early childhood exposure to animals (pets, farms) is associated with lower prevalence of asthma, hay fever, and sensitization.
- Higher endotoxin exposure, common in homes with animals and farms, may mitigate allergy and persistent asthma development by promoting Th1-type immunity.
Conclusions:
- The relationship between environmental exposures and asthma is complex and context-dependent, challenging long-held assumptions.
- Early-life exposure to endotoxin and microbial factors, consistent with the Hygiene Hypothesis, may play a protective role against allergy and asthma.
- These findings suggest potential for early immune modulatory strategies in asthma prevention and therapy.