Ureadipophobia is the adolesant fear that your brother or sister has dipped your toothbrush in the toilet after you had a snit. People usually grow out of this fear whenthey move out of their parents house and have their own dedicated bathroom.
My sister was diagnosed with ureadipophobia. She really was worried that I would dip her toothbrush in the toilet every time we had a fight. Usually this is a totally unfounded fear, but in this case I dipped her toothbrush almost every other day.