What is the cause of lice? other than people passing it on to you.

Lice begets lice: It was once famously said, "Lice begets lice." There is no other source of lice than another louse. We don't have an answer to the louse or egg question, so we don't know which came first. A person has to get a louse or an egg that hatches into a louse, in order to get infested. A louse can be on furniture, hair brushes, or clothing, but it most likely jumps from one person's hair to another's.

No other source: The louse (lice is plural) is a selective human only parasite. It cannot live on other hosts (like an animal).To get lice, you got it from someone who has it.It might pass through a shared comb or brush, hat or scarf,etc.