This study will assess the Aerogen Solo® (Solo®) vibrating mesh nebulizer as a potential new device for use in allergen challenge testing.

This will be a multi-center, randomized, cross-over study utilizing the expertise of three Canadian academic centers (University of Saskatchewan, McMaster University, Laval University) that have been performing allergen inhalation challenges and other bronchoprovocation studies for more than forty years.

Each participant will be required to attend the research lab on five occasions (Visits 1-5). At Visit 1, study staff will provide an overview of the study purpose and procedure and answer any questions the participant may have. The individual will then provide consent if they wish to participate (i.e. sign the consent form). Skin prick testing to determine relevant allergen sensitivities and to determine which allergen extract will be used for the skin test endpoint (STE) and allergen inhalation challenge will then be performed. The participant will be randomized with respect to which nebulizer (Solo® or Wright) will be used first. The choice of nebulizer for the first participant will be via blinded draw. Subsequent nebulizer assignments will alternate. Participants will undergo the STE procedure and methacholine challenge testing (MCT) at visit 2; an allergen challenge will be done the next day at Visit 3 using the same nebulizer as was used for the MCT at Visit 2. Visits 4 and 5 will also be performed on consecutive days and will involve methacholine and allergen challenge testing, respectively, using the nebulizer that was not used at Visits 2 and 3. A minimum of two weeks must separate Visits 3 and 4.

Inclusion Criteria:

• baseline FEV1 greater than or equal to 70%
• positive response to inhaled methacholine (i.e. PD20 less than 400mcg)
• evidence of atopy (i.e. positive skin prick test to an allergen that can be used for the inhalation challenge
• absence of respiratory infection for at least 4 weeks
• absence of allergen exposure (or other trigger of upper or lower respiratory symptoms) for at least 4 weeks
• current nonsmoker (ex-smoker allowed; case by case basis; investigator discretion)
• require only infrequent short-acting beta2 agonist (i.e. salbutamol or terbutaline) to treat/control asthma (i.e. no inhaled corticosteroid or combination therapies, no intranasal corticosteroid; anti-histamines etc.)
• general good health with no other medical condition, medication use or lifestyle activities that would influence the outcome of the allergen challenge

Exclusion Criteria:

• pregnant or lactating