A nebulizer is a medical device that allows infants or children to receive medication in the form of mist that is inhaled into the lungs, according to KidsHealth.org. Often it is used for asthma or other lung or breathing difficulties. The mist goes directly into the lungs to allow the medication to begin working right away. This method of medicine administration is especially convenient for infants who are too young to use an inhaler. With the right equipment, giving a nebulizer treatment to an infant can be simple.