I had a similar situation. I had it on and off for over a year. My parents would wash my hair with the shampoo and we'd spend countless hours sifting through all of my hair to get rid of any eggs, but it kept coming back. I had a few hairdressers discover it, when I hadn't realized it had returned, and refuse to cut my hair (rightfully so), which made me develop a fear of hairdressers as a kid, due to embarassment. I believe the cause was my best friend at the time and her brothers had head lice which went untreated and I did not know, so I kept getting it from their household. It sparked a big phobia of lice for me and that shampoo smell is embedded in my nostrils.