I gave my son dylsum cough med at about 4
Cough and cold are very common ailments in child Chat Doctor.  Most of the time it is caused by certain viruses. Usually it is associated with an allergic component and use of some antiallergic like cetirizine should help. Antibiotics are generally not required as they are ineffective against viruses. It should recover on its own in 5-7 days. Delay contains Dextromethorphan which is a cough suppressant and I would not advocate its use. Same about codeine which is also a cough suppressant. Rather use an expectorant which works just the reverse and helps in bringing out the cough. Steam inhalation should be helpful in diluting the cough. Generally moderate variations in dosage is tolerated well, and you need not worry about overdose. Remaining in follow up of a doctor would ensure that.