Do you take anything for it? Benadryl, and sometimes even Zyrtec (and their generic knock-offs) can sometimes knock you on your butt. The active ingredient in Benadryl is actually used as a sleep-aid. So that could cause it. But for me, yes, allergies do wear me out from time to time. I presume the whole "body fighting histamines" thing takes a toll on things like your immune system and probably helps with vitamin deficiencies. Heck, an allergy itself is commonly defined as some type of deficiency. So it stands to reason I suppose. But you are not alone. Hell sometimes I feel actually sick from allergies. Not runny nose sneezing kinda sick. Actually not even coughing or congestion sick (even though when its bad I do get lots of gunk in my lungs). But sometimes I just feel like the life is being drained out of me, and I have no motivation because I just feel dead