Take off and drug it from orbit. It's the only way to be sure.
Message I just sent to my allergist:
The singulair on its own is as near to non-effective as I can tell. 10mg singulair plus 20mg doxepin, thrice per day, seems to be more effective than the same dose of doxepin on its own, but is still only about 95% effective. Itching is mostly controlled, reduced to a mild annoyance; hives are still present, tho in lower density. However, the cognitive side effects of the doxepin, while not anywhere near as bad as they were last time I was taking it regularly, are really starting to bother me.