Do head lice like dirty or clean hair more?
Diana - The NHS claims that actually, yeah head lice do prefer clean hair, but we were talking about it earlier and from an evolutionary perspective, it seems to make much more sense that lice might have developed and evolved with humans before they'd invented shampoo. So I think it’s just as likely that they like dirty hair and I'm sure there are lots of people with filthy hair that have lice in their hair as well.
Dave - Unless of course we’re secreting something which kind of slows them down or makes it harder for their eggs to stick to hair or something. I don't know anything about this, but human hair oils might actually be quite good at slowing down head lice.
Chris - And your argument would be, if you wash the hair with shampoo, you actually wash away that natural protective effect and the consequence of that would be that the nit would find it easier to infest you.
Dave - Yeah.
Chris - In other words, if you've got clean hair.
Dave - And purely because we’ve been living with them for so long, it would make sense we’ve evolved in some way of discouraging them.
Diana - It’s quite possible.
adam asked the Naked Scientists: Do head lice like dirty or clean hair more? What do you think? adam, Tue, 23rd Nov 2010
Apparently they like to have both
To quote from the above reference (citing the work of Prof. Rick Speare, James Cook University, Townsville):
I think they are only concerned with a good blood flow, cleanliness is not an issue for them. Don_1, Wed, 1st Dec 2010