My 6 Year Old Son Has Been Complaining Of Dizziness

My 6 year old son has been complaining of dizziness often for the last few months. His vision is fine. He has symptoms of allergies most of the time. I have been giving him a daily vitamin of good quality this past week. His teacher has also brought it to my attention that he complains of dizziness. I have been telling him to drink water because I am not sure what could be causing this. Thank you for any suggestions.