Can i use a cool air humidifier for my 3 month old daughters cold?

Absolutely: The more humidity the better. Put the humidifier right next to her crib, not 20 feet away across the room. Extra humidity helps soothe the airways from nose to lungs, and thus decreases mucous production making breathing easier. Also use saline prior to use of bulb syringe if cleaning out her nose.

Maybe: In situations where the ambient humidity is low (heated house, winter , dry outside environment) it is quite helpful. In some situations, like an air conditioned house in the summer, it may offer little. Once the ambient humidity passes 50% house dust mites thrive, after 60-70% you can see mold growth.I encourage moms to have simple humidity gauge in the babies sleeping area to monitor that issue