Back in medical school a professor once said if there are a number of treatments for one illness that means none of them work terribly well.
Yesterday a nasty case of head lice came in the form of a ten year old girl with an otherwise beautiful head of thick brown hair. There weren't just a few knits, they were everywhere. Immediately everyone in the office who had any contact began to scratch their heads. My nurse bombed the exam room with a head lice spray and Lysol. We didn't use the room for the rest of the day.
Once the girl left the office, stories of infestations flew out of everyone's mouths as well as lists of medicines and home remedy their mothers used on their siblings (because no one fessed up to having it themselves). By the time I left the office yesterday the list of treatments for head lice generated included: vinegar, mayonnaise, olive oil (which apparently is easier to get out than mayo), combs, shaving, saran wrap, permethrin /malathion, and my personal favorite--Listerine.
Based on this professor's rule of thumb, none of these work terribly well, and most parents I've talked to would agree.