Headlice is EXTREMELY contagious, and takes extreme efforts to get rid of it. It went around our school twice this year and it was rampant. My ds was so lucky not to get it but my stepdaughter got it. You have to wash everything you own that is cloth (clothes, linens, jackets, stuffed animals, slipcovers...) in hot water, and for the things that cannot be washed in hot water, bag them in BLACK plastic garbage bags tightly for ten days. You will know you have it if you find little tiny eggs on the hair shaft. They usually start around the neck and could be clear or white in color. They are very tiny. Get a special comb from the pharmacy that is meant for picking out/looking for lice eggs. The eggs can transfer from one person to another person and live like that for a week or maybe more, then hatch, then you'll know you have it because you'll be itching like hell.
At our school, most people HAD to resort to the chemical treatment because it was the only thing that would work, after trying natural remedies. But not all chemical treatments are alike. I think the one that you want to avoid is Kwell because it can cause brain damage if you accidentally use too much.
The book "Natural Healing for Babies and Children" (Aviva Romm) deals with headlice and gives recommendations for getting rid of it naturally - basically it is a rinse you make with apple cider vinegar and thyme essential oil - it uses a lot of thyme oil, I think maybe a full ounce - which is expenise - we made up the recipe and the thyme oil cost around $17 - but worth it! You shampoo it in your hair every night, then rinse it out. Also you are supposed to rub olive oil or coconut oil into your hair, cover it with a scarf or bandana, and leave it on all night. Lice don't like grease. Washing your hair with shampoo will not help! They like the clean hair shaft. They do not like grease so get your hair good and greasy with olive oil. Good luck!!