Symptoms of liver problems symptoms and conditions

I am a 60 year old man who has had allergies and asthma as long as I can remember. I've tried most of the medicines out there at one time or another. I hate the side effects of most asthma meds (especially broncodilator inhalers) and have learned to avoid them and manage my symptoms more through lifestyle (diet, exercise, clean environment) than drugs. I decided to try Singulair starting about 3 months ago to see if it would help with the mild night time chest tightness I would often still experience. I have to say its the best asthma med I've ever taken. I am about 90% free of asthma symptoms, and can sleep through the night without ever waking up with constricted bronchia. I don't use inhalers at all any more. Occasionally (2-3 times a week) I'll take a Claritin if I start to feel allergic symptoms breaking through. The only side effect I've noticed from the Singulair - and I noticed this from day one - is extremely vivid dreams. Luckily, I kind of like this side effect so I'm OK continuing with the Singulair. Also luckily, I've never experienced the aches and pains, weight gain, or other symptoms descibed by others on this site. The one thing I worry about is that this drug may be hard on the liver, as the liver metabolizes it. But since I don't have any symptoms of liver problems, I guess I won't worry too much.