Is It Safe Giving Amoxicilin With Montelukast To Child For Allergic Rhinitis?

My son who is 25 klos, turning 6 this month has an allergic rhinitis and has this very irritating sound that he produce, like ahem . An he makes that sound almost every second for a week now. His pediatrician gave him montelukast for 1 month levocetirizine (xyzal)and some gargle solution (orofar). And after 7 days, he still have hat sound which I really think is starting to become a habit because he never had that sound when he sleeps. And now he has a hard cough. Is it safe to give him antibiotics - amoxcicilin at the same time? he already finished his levocetirizine so he only takes montelukast every ight and gargles 3 times a day. Thank you so much