What Causes Severe Cold And Blocked Nose In A Toddler?

My son who is 4 -yrs-old has been diagnosed with primary complex last week. We took him to a pulmonologist who has prescribed him 1) R-Cin suspension 5 ml & 2) Isocaldin suspension 10 ml in the morning for 6 months. He has also given 3) Metozinc syrup 5 ml in evening & 4) Atcef-AZ tablet to be taken 1/2 in morning & 1/2 at night At present my son is having severe cold and blocked nose. Can I give him cetrizine syrup 2.5 ml in morning and night, to cure cold. Pls, reply as we are not able to contact his Dr