Allergies can CAUSE exhaustion, you know. That and the brain fog are really my most debilitating allergy symptoms. But I agree, if they're affecting you that badly, it might be time to see about immunotherapy. Or at very least a scrip for Singulair (leukotriene blocker), which deals with those symptoms much better than antihistamines do. It's way cheaper since it went generic a year or two ago.