We recently received the oft-dreaded email from our son’s school informing us of a case of head lice in his class. It said, “A child with an active head lice infestation likely has had the infestation for 4-6 weeks and therefore poses little risk to others, especially given the low contagion within classrooms.” This struck us as strange, given the anecdotes we hear about the rapid spread in certain grade levels, and also led to a disagreement about whether or not to use a preventive spray each morning on our son’s head.
We’d love to get your take on two questions: (1) what does the data actually say about the spread of lice in classrooms? and (2) do any of the preventive sprays or other measures actually work?
—Feeling itchy
I feel you. There is nothing that gets you itching faster than the threat of lice. I literally scratched my head as I was writing this.

Your child’s school is following American Academy of Pediatrics guidelines — indeed, I think it has quoted directly from the AAP (you can read the whole policy here). Children are not excluded from school due to lice. There are few pieces to the logic here.
- Lice spread mostly by jumping between human heads. The heads have to be touching and, also, this mostly happens if there are a lot of lice. If there are just a few lice, they like to stay on their home head. This can happen in classrooms, of course, but it’s not that likely unless kids are constantly sharing headbands or hats or some other hair product.
- Once active lice are noticed on a child (usually due to the itching that is driven by louse saliva), they can be quickly treated and killed. At this point, there would be no reason to exclude a child from school.
- It used to be policy to inspect all children for nits — that’s the lice eggs — and have them stay home from school and get treated if nits were present. Research has shown, however, that only a relatively small share of these nits turn into lice, so this policy excluded (and shamed) a lot of kids for no reason.
Putting these points together, the school policy on lice tends to be that you have the kid with the active lice treated and you ask other parents to keep an eye on their kids. Preventative sprays are not generally recommended. Just watch your kid for nits, and try not to give into the phantom itch.
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Can you say more about “preventative sprays are not generally recommended”? We have a lice prevention shampoo (Fairy Tale brand) with citronella, tea tree, and rosemary. Is there any indication that might help prevent lice?