The most commonly reported side effects were: oral thrush , nausea , headache , and pain in the pharynx or larynx . More rarely reported side effects (occurring in <1% of patients during the clinical trial) include: tachycardia , palpitations , dry mouth , allergic reaction ( bronchospasm , dermatitis , hives ), pharyngitis , muscle spasms , tremor , dizziness , insomnia , nervousness , and hypertension . Patients experiencing an allergic reaction or increase in difficulty breathing while using this medication should immediately discontinue its use and contact their physician. 
Sixty-five trials met the inclusion criteria for this review . Fifty-six trials (19 paediatric trials) contributed data (representing total of 10,005 adults and 3,333 children); 21 trials were of high methodological quality; 44 were published in full-text. All trials pertained to patients with mild or moderate persistent asthma. Trial durations varied from four to 52 weeks. The median dose of inhaled corticosteroids was quite homogeneous at 200 µg/day of microfine hydrofluoroalkane-propelled beclomethasone or equivalent (HFA-BDP eq). Patients treated with anti-leukotrienes were more likely to suffer an exacerbation requiring systemic corticosteroids (N = 6077 participants; risk ratio ( RR ) , 95% confidence interval ( CI ) , ). For every 28 (95% CI 15 to 82) patients treated with anti-leukotrienes instead of inhaled corticosteroids, there was one additional patient with an exacerbation requiring rescue systemic corticosteroids. The magnitude of effect was significantly greater in patients with moderate compared with those with mild airway obstruction ( RR , 95% CI , versus RR , 95% CI , ), but was not significantly influenced by age group (children representing 23% of the weight versus adults), anti-leukotriene used, duration of intervention , methodological quality, and funding source. Significant group differences favouring inhaled corticosteroids were noted in most secondary outcomes including patients with at least one exacerbation requiring hospital admission (N = 2715 participants; RR ; 95% CI to ), the change from baseline FEV 1 (N = 7128 participants; mean group difference ( MD ) 110 mL, 95% CI 140 to 80) as well as other lung function parameters, asthma symptoms, nocturnal awakenings, rescue medication use, symptom-free days, the quality of life, parents' and physicians ' satisfaction. Anti-leukotriene therapy was associated with increased risk of withdrawals due to poor asthma control (N = 7669 participants; RR ; 95% CI to ). For every thirty one (95% CI 22 to 47) patients treated with anti-leukotrienes instead of inhaled corticosteroids, there was one additional withdrawal due to poor control . Risk of side effects was not significantly different between both groups.