My baby is 3 month old and sometimes makes sounds through nose like taking the mucus inside like how actually cold infected people do. But when I observe I can't see any mucus in nose and not even runny and no cough also. Only once or twice in a day he coughs or no. How can I conclude it's cold or not. Initially I have given saline drops as he makes that sound but no use. What can I do for this. If it is cold he is getting releif for 2 or 3 days when I give saline and syrup and again repeats.