Hi, My name is Corey. I am allergic to cats and dogs and after trying multiple allergy meds with my doctor i found that 10mg of cetirizine works when I visit houses with pets. However, I am now staying with some family that have pets for a few weeks and after about 10 hrs the cetirizine starts to wear off and I cant be in the house. I was wondering if I can take a second 10mg tablet in the evening to help while I stay with family.