Does Singulair cause a lactose reaction?

I have chronic post nasal drip and cough, pain in front of head and sinuses and sometimes a 'wheezy' throat (and generally being worn out).
Things that I find seem to make it worse are eating anything with milk in, dust, car fumes, cigarette smoke & animals.

Recently been to see my Dr. He suggested Singulair which sounds great but I am worried because it has lactose in. So far I have taken it for 2 weeks the pain has stopped but the post nasal drip and cough continue. I also have developed sore dry lips.

As Lactose and anything to do with milk products is some thing I usually avoid as it makes my symptoms worse, is it likely that is it causing a problem in the Singulair?

[Tammy2009]

It is possible.  They say that there isn't enough lactose in them to react but I disagree because I've noticed a difference as well.

The only difference is I noticed the difference going from symbicort to advair HFA, I don't get as much muscous unless I'm having a asthma flare-up.  

You could try just a regular antihistamine without lactose but it may take a bit longer for your sinuses to drain out all the gunk they have in there.  I probably would continue using it for a couple more weeks and then reassess the symptoms.  Also think about acid reflux being a component since the symptoms are the same.