From your message, you appear to have an intolerance to the so-called non-sedating anti-histamines but hopefully will be able to
take Singulair;
it is a good drug
for nasal allergies and also,
for a fair number of people, effective treatment for asthma. And it is safe, not a cause of significant liver disease, and not associated with other side effects, deemed serious.
To the best of our current knowledge, the long term use of a nasal steroid, as directed, does not pose a problem.