There is no approved cough medicine for children under 6 due...

...to the drugs that are found in over-the-counter cough syrups.  The best cough syrup for kids between the ages of 1 and 6 is a liquid blend of ivy and thyme.  During a cough, asthma, cold or flu, a teaspoon of ivy/thyme syrup a few times a day works wonders.