Nose polyps. Of hay fever or pollen?

Hi Greetings, Trust you are doing good. My kid was suffering with Nose ployps from last 2 Months, We have consulted some General Practician and he has prescribed "cetirizine hydrochloride" which we had given to kid for 20 days and could see no improvement. And the nose polyps are growing back when there is windy or cold weather especially night blocking the nose which made kid difficult to breathe night time this effecting kids sleep. As we know nasal steroids spray many not be good for kid, we are looking to understand what would be the best treatment available for kids without much side effects. And this could be because of hay fever or pollen? And the kid poo also giving a lot of foul smell we can't even stand nearby when his toilet time ...and from last one year he poo's only once in two days, not sure if this is related here... Appreciate your kind response on this.