LiceDoctors is adamant on this topic: You do not need to spray your house to eradicate head lice!
Your Child Has Lice
You have found head lice on your child’s head. You are very anxious to get rid of them ASAP. You are wondering what you need to do with the house. You figure that you can get rid of the lice in the hair, but you are worried about your child getting lice back into the hair from her bed, dolls, or clothes.
Worry not! It is not at all likely that you will be re-infested from bugs in your house. Lice do want to leave your head and reside on a piece of clothing or furniture. They need blood to live; they also need the temperature of the scalp to live. Basically, there is no enticement for bugs to leave the head and hang out in the house. Nits (eggs) are stuck on the hair and rarely fall off. If they do manage, somehow, to detach from the hair, they can NOT reattach on the hair. Nits off the hair and basically useless and will die shortly.
Spray for Lice in the House?
NEVER spray in the house. Pesticides may have toxins and it is totally unnecessary to spray since a) there will likely be no bugs in the house b) if there is a bug, it will die within a few hours off the head anyway.
If you talk to a lice professional who says they will charge you to exterminate in the house, run for the hills. That is a scam! Head lice are not like bed bugs—head lice do not need to be attacked off the head. Concentrate on the scalp and you will be attacking lice at the source where they live. That is the only way to eliminate a head lice infestation.