Allergies

My 6 year old son has been struggling with allergies for about a year now. I was hoping once winter started, they would calm down but it hasn't changed much. We do Flonase, an allergy pill in the morning and we were doing benadryl at night but it didn't help much and now he has a cough so we've been giving him cold medicine. I've been to his primary, we've taken him to the express cares in town. They all say allergic rhinitis and pretty much just keep doing what I'm doing. We run a humidifier at night, he's got two pillows so his propped up while sleeping. It's keeping us (everyone in the house) up at night because of his constant sneezing and coughing and the poor kid can't get any rest. We have no pets in the house and I clean regularly. Does anyone have any recommendations or suggestions? I am open to pretty much anything at this point. Thanks in advance!