http://www.medications.com/effect/view/28187 I have severe allergies. They are so bad, my ears hurt and I have massive headaches. I thought I had sinus problems as well. My new doctor said it wasn't sinus problems, but my allergies got worse. She put me on Singulair. It took a week for it to get in my Thu, 20 Mar 2008 01:21:06 -0400 http://www.medications.com/effect/view/28187?item=5674 I don't think weight loss is a side effect of taking Singulair. Look at this page which says about the side effects of Singulair. http://www.internationaldrugmart.com/singulair.html http://www.medications.com/effect/view/28187?item=5674