3 Year Old Son Having Urinary Frequency

Just wanted to report that my 3 year old has been on Singulair for 3 days for severe seasonal allergy symptoms (which I must state he is having for the first time in his life). Today he began urinating very frequently and is not drinking more than usual. He also has a huge appetite. As his allergies had gotten so bad to include extremely swollen eyes/scleras and nasal congestion, we decided to continue the Singulair unless I begin to notice other adverse side effects. My daughter had taken Singulair when she was about 4 and we stopped it after she had 2 nights in a row of bedwetting which she had never had since she had been potty-trained at 2 1/2. I hope to have him off of it in the next couple weeks and only reserve this as treatment for the worst of allergy symptoms as all of the possible side effects concern me very much.