14mth old boy had head cold now chesty cough at nigh/phlegm drips down throat. nose running brown/yellow mucus. been 7 days. when see a doctor?

Productive cough: Make an appointment for your child to be seen as soon as possible. He may need antibiotic treatment.

Post nasal drip: Your child may have a viral infection which typically can take 10 days to clear up. If there is a fever, problems breathing or any pain, I think he should be seen right away. Keeping him well hydrated, using nasal saline and gentle suction and a mild decongestant for children at night will help to alleviate his symptoms. If the cough lingers more than 3 weeks, he should be seen for chronic cough.