The asthmatic airway is identified and studied using inhaled agents such as histamine and
methacholine. The use of antihistamines prior to the test will inhibit the test result if
histamine is used to cause airway constriction. If using methacholine, this may also be true
depending on whether old (e.g. benadryl) or new (e.g. desloratadine) antihistamines are used.
This study will look at the effect of old and new antihistamines on inhaled methacholine
challenge response in individuals with mild asthma.