2sickkids, I think it would be worth getting the full Ambry panel of genetics. If you have DF508, you could very well have another, less common gene which would explain your health problems. Getting treated properly could make a huge difference in your health. It only takes 2-3 wks to get the results back. I'd do it for your children. Other thing, on the zyrtec, YES, it most certainly can dry up the sinuses. Our ENT is insistent that our children ONLY use zyrtec or extendryl (an antihistamine/decongestant/anticholinergic) when they're having obvious allergy symptoms, CLEAR runny nose, itchy/watery eyes, etc. If they're congested, we drop zyrtec, use extendryl if we have to but just trying doubling up on nasal washes and nasonex, use an OTC decongestant like sudafed and sometimes afrin for no more than 3 days.