I have never heard of singulair and zyrtec causing that much weight problem. Flonase can cause some weight gain, but not that significant of one. I say you should talk to your doc about this. My only weight gain problem has been with oral steroids, and still it's only been about 10 or 15 lbs at most. You may also consider seeing a nutritionist. Aside from that, if you really do wanna' switch your asthma/allergy meds there are other medications that are similar to the ones you're taking. Singulair is a leukotreine modifier. There is another one in production that is similar and that is accolate. Usually, though, accolate must be taken twice a day, whereas singulair should be taken once a day. Flonase is a nasal corticosteroid and it's similar is nasonex. Finally, Zyrtec is an allergy/antihistimine medication and there are several of those out there (allegra, claritin, clarinex, etc). Honestly, IMO, the weight problems (if they are indeed your medications) are worth the breathing...