Montelukast (for asthma) and desloratadine (for allergies) are effective therapy for their current uses. Part of what happens when your allergies trigger your asthma should be prevented by either of these drugs. This project is being conducted to determine if these drugs are effective, either alone or in combination, on controlling asthma that is triggered by allergies.

Inclusion Criteria:

• baseline FEV1 > or = 65% predicted
• positive methacholine challenge (i.e. methacholine PC20 < or = 16mg/ml
• positive allergen challenge

Exclusion Criteria:

• negative skin prick test
• lung condition/disease other than asthma
• currently use montelukast and/or desloratadine