Can Nosebleeds Be Caused By Piriton?

Hello. My 11 year old son has terrible runny nose due to allergies. 4 days ago, he had a fever of 38 deg, and has also developed a cough. I have taken him to the MD and was prescribed antibiotics, flu and cough meds. He is now back to piriton but has terrible nosebleed after taking them. This has happened for 2 nights now and I m worried sick. He has missed school for a week now. I want him to have fully recovered before going back next week.