My 10 year old daughter was prescribed Zyrtec for cat/dog/other allergies in the spring of 2004. She had severe emotional outbursts, to the point we were considering doing counseling. She was angry, arguementative, extremely tired and suffered from insomnia. We took her off when her allergies subsided. ALL of her behavior issues have been non existent. We didn't realize until this month when she started it again that her behavior changes coincided directly with taking the medication. We have our daughter back!