Nonselective β-adrenergic antagonists, such as propranolol and timolol, are competitive antagonists of catecholamines at the β1- and β2-adrenergic receptors (β-ARs). β2-AR blockade may result in hypoglycemia as a result of decreased glycogenolysis, gluconeogenesis, and lipolysis. Moreover, bronchial hyperreactivity is a direct effect of nonselective β-blockers, resulting in bronchospasms due to pulmonic β2-AR blockade. A solution to minimize many of the side effects of nonselective β-blocker therapy may be the use of more selective β1-blockers such as metoprolol or atenolol, which, at low dosages, have little β2 activity. Unfortunately, there is a paucity of clinical data comparing the efficacy of selective and non-selective β-blocker. Furthermore, because of the broad heterogeneity of IH (e.g., proliferating versus involuting), confounding with other pharmacologic exposures (e.g., corticosteroids), associated complications (e.g., ulceration) and comorbid medical anomalies (e.g., PHACE) that can influence efficiency after IH treatment, observational studies are unable to definitively establish the clinical utility of β-blockers in IH. Thus, questions regarding the efficacy of the subtypes of β-blockers must be answered in randomized controlled trials, which may provide the only way to overcome the selection and ascertainment bias.