I have been on Singulair for a little over a month now and my allergies and asthma are under control; however, I have a list of side effects that are a mile long. I have swollen, bleeding gums, bad nightmares, weight gain, severe bruising, hearing things that aren't there, severe fatigue, confusion, can't seem to remember anything, dizziness, sore muscles, change is stool color, joints have swollen and sore, sexual desire gone, headaches, ears ring. I have stopped today and have called my doctor about the bruising. It's a shame because my allergies and asthma have almost completely dissappeared.