I am 30 years old, adult onset allergies, and I went three years taking allergy shots, steroids, singular, advair, and normal anti-histamines. I was probably going through about a big box of tissues a week (at least). Nothing made me better and I was a mess. Bronchitis all the time, blowing my nose constantly and having sinus surgery every few years to clear everything out.
Zyflo is the only drug that has worked for me. I would definitely only consider it if singulair is 'not enough' mucous reduction for you, if you're still coughing stuff up. It is 100% metabolized through the liver, so this is why you have to get your liver enzymes checked- and it's every 3 months, not every month unless you are on other liver meds or have liver problems. The pills are the size of most anti-biotics. You get used to it. Also, you can also take 1 every 6 or 2 every 12 hours. It's prescribed both ways.
I feel like I have gotten my life back. I don't snot everywhere, no sinus headaches, no bronchitis, no steroids in 3 years now, advair dose is decreased, and I haven't needed surgery.
If mucous is your problem, this drug is for you. The blood tests every 3 months and decreasing alcohol intake is well worth it. It's also really expensive, but my allergies and sinus problems no longer rule my life anymore. Well worth it.