Thank you for your query on Healthcare Magic.
Frequent and prolonged cough
may be due to allergy, asthma, or lower respiratory tract
X ray chest will rule out any underlying lung problem.
His lungs has to be examined by the doctor to look for wheezing and lower respiratory tract infection.
Investigations like x ray, ESR, absolute eosinophil count
to be done to rule out underlying problems.
Consult the Pediatrician
for examination and evaluation.
Hope I have answered your question.