Safety. Both provide humidified air to help soothe the airways. Doctors frequently recommend the cool mist humidifier because there is no fear of safety concerns. Vaporizers use heat to vaporize the air and produce very hot steam from the opening. A child could burn themselves in this way or by accidentally pulling on the cord or turning over the unit with risk of serious burns. Safety first always!
Cool for cough... Cool mist humidifiers can provide welcome soothing relief for inflamed, irritated bronchial tubes & its companion confounding cough; whereas, hot vaporizers act to "melt" the mucous clogging sinus passages. Think "c" for "cough" & "cool mist". Think "h" for "head"(congestion) & "hot" vaporizer. If unsure, c wins over h! beware, some vaporizers may generate enough heat to actually burn your baby.