Wendy,
DD also has several allergy issues and has been in treatment with an Allergist for 1 year. The first thing he prescribed us was Singulair and she took it for about 4 months. It was hell. DD suffered from extreme behaviour problems: she went from being a normal spirited child to throwing 10 fits a day, she would tell me repeatedly that she was sad, that she wanted to cry, she couldn't handle anyone "contradicting" her (I would give her juice in a red glass and she would throw it away crying desperately that she wanted the blue one), she would be crying one moment and laughing the other... it was hell for me. I felt like I was failing raising my child. One day, the Allergist called me and asked me if I had noticed a change in DD's behaviour (if she had turned violent, specifically) because he had received a warning from the FDA about the side effects of Singulair. As soon as I hanged up the phone, I went and Googled about it and the results were horrible. I took her off Singulair immediately and felt like the worst mother in the whole world. DD went back to her normal self after 1 - 2 weeks.
I beg you to read about the side effects and make an informed decision whether to give your LO that medicine or not.
DD is also allergic to dust and mold, and has suffered from Sinus and Rinitis and at the moment we are treating it with a spray called Rinalin and 2 inhalers - Ventolin and Becotide. It has done the trick for already 2 months. We keep her room with very little furniture, no carpet, we wash the curtains every 2 weeks, no pillows or stuffed animals allowed in her bedroom and we dust and clean the house everyday whenever DD is out of the house, and we are considering buying an air purifier for DD's room, but I am still not sure how much it will help, since I won't keep DD in her room 24/7.
Another approach that helped us a lot was taking her to a clinic where they practice Biological medicine. There, they performed a test called BICOM where they made me take a sample of EVERY food that DD eats, samples of household cleaners used at home and samples of the paint, dust and anything I could take and I found out that although DD didn't test allergic to a lot of things in the traditional allergy test, she proved to be "sensitive" to a lot of food. I stopped giving all those things to her and her condition has improved. I feel that although she is not 100% cured, she is more "resistant" now and she doesn't fall into crisis that easily.
I hope I haven't bored you with all this, and I urge you to take a deeper look into Singulair.
Take Care.