Headaches in 11 year old. Needs focus.

Recently my kid is complaining of mild headaches for past 1 month. It's like mild to moderate and happens mostly in the evenings. Occurs once every 2 or 3 days. It subsides like in couple hours n he sleeps after that. when he has those headaches he can't do anything that needs focus. He has to relax like watch some cartoon. What could be causing these headaches. Need help Background: he is also having some allergy n dry eye issue like past 4 months. Couldn't figure out the reason yet. Opthamalogist has put him on eye drops (antihistamine and tear drops). His medication changed like a month back. I'm not sure if there can be any connection but just giving a full picture. He is an otherwise healthy n active child.