Proximity to traffic, particularly to diesel-powered heavy-duty vehicles, has been associated with inducing and enhancing allergies in children and adults. To investigate the basis for this association, a controlled exposure of allergic rhinitics to diesel exhaust was performed at a dose known to be pro-inflammatory in healthy individuals.

The hypothesis was that airway inflammation would be augmented in allergic rhinitics following exposure to diesel exhaust at an environmentally pertinent particulate matter concentration.

Fourteen allergic rhinitics were exposed in a double-blinded, randomised trial to both diesel exhaust at 100 microgram/m3 PM10 (representing an aerosol of nanoparticulate combustion particles, mean diameter 80 nm) and filtered air for two hours on separate occasions. Bronchoscopy with endobronchial mucosal biopsies and airway lavage was performed 18 hours post-exposure, and samples were analysed for markers of inflammation.

Inclusion Criteria:

• History of seasonal allergic rhinitis requiring medical treatment only during the pollen season and were classified as mild and intermittent according to ARIA guidelines.
• Positive skin prick test to airborne allergens
• Normal lung function
• Negative Metacholine challenge

Exclusion Criteria:

• Current smoking or a previous history of smoking.
• Asthma
• Chest infection within six weeks prior to or during the study
• Current use of non-steroidal anti-inflammatory drugs
• Current vitamin C or E supplementation
• Current use of topical nasal steroids.