The bottles of lice treatment shampoo have very clear warnings NOT to use as a preventative measure only for full blown infestations ... they are highly toxic you do not want to apply that to your skin just as a precaution and if you DO and they do not have lice yet you risk if you DO get them having them be 'resistant' to the treatment!

I second or third the suggestion of using a TEATREE oil as a preventative measure ... I have used this weekly on my hair for all the decades I have been in the field and we have never had lice come through our home despite having had it in centre year after year and being 'exposed' to it ... but even Teatree oil while 'natural' is still harsh plant do not use it more than 'necessary' to prevent lice or as a treatment for it ... aka I would not use it daily preventative cause the plant has been shown to be hard on the kidney's when constantly exposed to it