"I have no lung capacity."
Do you have asthma? I am not clear about what you mean by the above statement.
Most allergy sufferers will have nasal congestion and sneezing and watery, itchy eyes. If you are feeling problems with you lungs, perhaps you also have some element of bronchospasm.
If you are really disabled by it, should should really try and find a good physician who would be willing to work with you on it.
Claritin is a very safe, well-tolerated medication. If 10 mg daily is not working, you might try taking 10 mg twice a day. It is safe. Take it on a regular basis, every day, not just now and then.
Singulair - make sure you are taking it every single day. It is more effective if you take it at bedtime.
Long-acting nasal steroid, such as Flonase - again, use it every single day, in the amount recommended by your physician.
You might also ask your doctor to give you a trial of inhaled steroid, such as Flovent, and also a trial of an Albuterol inhaler that you can use on an 'as needed' basis 10 minutes of so prior to running.
You can try saline nasal irrigation using something like the NeilMed Sinus Rinse. If you try this, do it prior to using nasal steroids, not afterwards.
And you can also try running with a surgical mask on, and with wrap-around sunglasses, to try to decrease allergen exposure.
Lots of options. Probably nothing will totally eliminate symptoms, but they can certainly be diminished.