Poplar trees symptoms and conditions

My daughter is a 4 year old child started on Singulair after she was unable to tolerate Zyrtec. For the first few days her allergies seemed better and we were encouraged by her improved allergy symptoms (allergies to poplar trees, grass, and lambs weed manifest as headaches, itching (usually of the extremities), and stomach aches). However, after 2 days her behavior became increasingly erratic. She was emotional, tantrum prone, irritable, anxious, and had difficulty sleeping although she appeared and said she was exhausted/tired. After several weeks on Singulair, we stopped the medication to determine if it was causing the behavioral and sleep problems. The symptoms stopped after discontinuing Singulair and she went back to her usual happy, well behaved self. After being off of it for several weeks we decided to try it again due to her allergies flaring up and wanting to be sure it was the Singulair causing the behavioral problems (because for all of its negatives, the greatest positive about Singulair is that it definitely helps her allergy symptoms). Unfortunately, the irritability, anxiousness, tiredness, tantrums and insomnia returned. We tried giving it to her at different times during the day but the symptoms were still present (although she slept a little better when we gave it to her in the morning). We also tried cutting the dose in half and giving it to her around noon. Decreasing the dose did help with the symptoms to some degree, but they were still bad enough to outweigh the benefits of taking the drug. As a nurse, I love Singulair for the relief it provides allergy sufferers...unfortunately for my daughter, the side effects outweigh the benefits. Given the rates of ADD, ADHD, and other behavioral problems diagnosed in children nowadays, I thought it pertinent to report these symptoms present in my daughter that are solely caused taking this medication.