Background: There is a perception by some asthmatic patients that stimulation of respiratory mucous production by cow milk may worsen airway obstruction.
Objective: To determine whether cow milk ingestion reduces bronchial airflow in asthmatic patients as measured by standard spirometry.
Methods: Twenty-five atopic adults with mild asthma but no history of cow milk allergy or lactose intolerance participated in a prospective, randomized, double-blind, placebo-controlled crossover study. Subjects were randomly assigned to ingest either a solution containing cow milk powder or a placebo solution, received neither during a 14-day washout period, then ingested the alternate solution. Forced vital capacity (FVC), forced expiratory volume in 1 second (s) (FEV1), and FEV1/FVC were measured at 30 minutes, 1 hour (h), and 7 hours after challenge. A > or = 20% decrease in FEV1 or FEV1/FVC was considered clinically significant.
Results: FEV1 was slightly lower at 30 minutes than the baseline value (mean change, .6% to 3.3%) for both challenges. None of the subjects experienced any adverse symptoms, acute or delayed, after cow milk or placebo challenges. Statistically significant changes in FEV1 were reached 30 minutes after cow milk challenge (P = .0007) and at one hour after placebo (P = .0027). These changes are not clinically significant.
Conclusion: Although this study disclosed no acute or delayed asthmatic symptoms or deterioration of pulmonary function detected by using conventional spirometry, methacholine inhalation before and after cow milk challenge may be more sensitive for evaluation of cow milk-induced bronchial hyperreactivity.