That's what prevents bacteria from accumulating, and there's more than one way to do it. Take the child in the shower or in the bathroom with the shower on and steam those little noses. Keep those secretions thin and moving. Hose the little noses with saline nasal spray and a nasal aspirator. You may reach for an over the counter cold medicine to help keep air passages clear, but don't rely on them too heavily.
Overuse can make some symptoms worse.
And there are other guidelines to keep in mind. The best time to use an over the counter medicine is at bedtime, to help your child sleep. Use the medicine cup, dosing spoon or dropper that comes with the drug. Don't reach for a spoon from the silverware drawer, you may accidentally give too little or too much. Don't use just any multi-symptom cold remedy.