Well the way my doctor has me double up is i'll take Clarinex which is a 24 hour antihistamine in the morning & Benadryl at nite. Usually I do this if my allergies are keeping me from sleeping, like a real bad rash or coughing like crazy. It helps, I really like Benadryl the best, but makes me sleepy so I can only take it at nite. Maybe you can try that. Sounds like you should try something like Singulair, b/c I would be worried about overdosing if I were you. Singulair is another allergy medicine that is not an anthistamine, but an anti leukrotiene. It helped me tremedously when I took it. Might be something worth looking into.