I found out few years ago that I have a multitude of allergies. About 20 (yes that's right) are food allergies, the remaining 20 (yep that's right too) are inhaled antigens. When I choose to partake of foods I know I'm allergic to, I expect to feel like crap for a few days. But it was very enlightening to be diagnosed. Once I stopped eating the offending foods and started on shots I felt like a new person. Before that I suffered from almost constant fatigue. Now if I start feeling run down I can think back to the exposures I've had and it usually makes sense.
I recommend getting a full scratch test done. It is unlikely that you're allergic to just one thing. Might as well go the distance and know what your triggers are ahead of time. Most asthmatics have allergies, and many who develop allergies will develop asthma.
Good luck, and give your body time to recover.