Your daughter as a girl in the age bracket between 8-14 belongs to the group that statistically has the highest risk of catching head lice.
If we ignore for a moment the “yuck” factor and the itching, head lice are interesting creatures. They remain on the head of “their” human and have a little blood snack every few hours. They don’t voluntarily leave their host and if they have the misfortune of falling or being brushed off, will die in little more than two days maximum. If another human comes close enough that the heads - and the hair - touch, they might decide to wander over and and settle there.
This is actually the reason why in modern societies head lice are the bane of schools and kindergartens, where children play in close physical contact, with heads touching during play, while reading etc. This might also be the reason girls have them more often than boys. And of course the children bring the lice home and can share them with us when we, for example, cuddle.
Contrary to popular belief, head lice are not an indicator of poor hygiene, there are even some statistics that suggest lice prefer clean hair.
Also, as lice don’t actively leave their host unless they can directly wander over to the head of a new human. basically all infections happen via touching heads. The risk of infection via bedding, clothing or furniture is nearly zero1 - and only if items touching the heads like hairbrushes or hats are directly exchanged and used is there a small, chance of a random adult female louse being transported, e.g. on a fallen hair, to a new human host.
But why all this explanation?
Because your daughter didn’t catch lice because her dad’s house was dirty. She has gotten them from a human that is infested. This might be her father, but it may also be a friend. In every case, someone she came in close physical proximity, with touching heads or hair. And in some people, the lice can go unnoticed for quite some time, not everyone reacts with the same intensity of itching to the bites and sometimes the itching starts as late as four to six weeks after infestation. And apart from the itching (and sometimes secondary infections from excessive scratching), head lice are indeed harmless. They take a few drops of blood, but unlike other parasites, they don’t transmit diseases.
The advice for your daughter would be to be aware of the way lice are transferred - and if she wants to be “safe” in an environment where she is afraid, to avoid physical contact like hugging and leaning heads together. (Don’t we immediately think of two teenagers sharing one set of earphones or looking at a smartphone screen here?) Just in case, taking her own pillowcase can perhaps make her feel safer (wash at 60C, put it in a dryer for 15 minutes or simply let it air out a few days after coming home), even if the effect is probably more comforting than protective.
And you or your daughter should talk to her father about the topic. The general rule is that if one family member has lice, it’s quite likely that others have them as well - everyone should be checked and, if necessary, treated. (Yes, that includes you!) If the rest of the family appears lice-free while your daughter has them, you might want to talk to her (close) friends. Depending on your local regulations, you might even have to inform your daughter’s school. The important part is that all patients with lice are treated, otherwise you can get an endless cycle of re-infestations and, in the worst case, a lice population that develops a resistance to the standard over-the-counter chemicals.
For details on proper treatment, seek the advice of your local pharmacist or pediatrician and follow the instructions that come with the product you choose. Without going into the health aspects (off topic here), a combination of chemical treatments and physical removal (lice comb!) and at least two applications eight to ten days apart are recommended.
1 see for example:
- CDC's website on lice
- this Australian study about lice in pillowcases
- this Australian study showing that lice don't crawl around haphazardly