The purpose of this study is to determine the effect of cetirizine, an oral antihistamine, on wheezing in patients with allergic rhinitis. Patients presenting to the pediatric emergency department who have a history of allergic rhinitis and who are wheezing will be asked to participate. Half of patients will receive a dose of cetirizine and the other half will receive placebo and their response will be monitored over the course of their emergency department visit with vital signs, physical examinations, and measurement of bronchoconstriction with spirometry.

This is a prospective randomized, placebo-controlled trial to look at the effect of cetirizine on bronchoconstriction in patients with allergic rhinitis who present to the Pediatric Emergency Department with wheezing. Oral second generation antihistamines such as cetirizine are already the standard of care for allergic rhinitis. Wheezing pediatric patients with allergic rhinitis who are not already on this therapy will be randomized to receive either age-appropriate-dosed cetirizine or placebo in addition to standard asthma therapy at the discretion of the treating clinician, and will be monitored every 30 minutes with asthma scores and FEV1 measurements. At the conclusion of 3 hours, each patient who received placebo will receive a dose of cetirizine, and each patient who received cetirizine will receive a placebo medication dose, such that initiating therapy for allergic rhinitis is delayed by no more than 3 hours.

Inclusion Criteria:

• History of allergic rhinitis
• Wheezing

Exclusion Criteria:

• Use of antihistamine within the past 72 hours
• Chronic Pulmonary Condition other than asthma
• Other contraindication to cetirizine
• Severe asthma exacerbation requiring resuscitation

The medication and placebo doses will be prepared in the pharmacy at the study site and provided to the investigators in deidentified bottles.