Pillow protectors symptoms and conditions

I just came back home from the dr. We made some tests and my 5 years old daughter is allergic to house dust mites and has beeing diagnosticated with athopic asthma. The dr. prescribed Singulair. Now, after reading all the posts, I freaked out and I have not idea what to do. I am really sorry I did't ask about side effect, but I considered, her beeing a dr, knows better than me. My thought now is: I'm not going to give my daughter Singulair.