Hi. This is a LOOONG reply. For most peolpe, this information isn't important, but I feel if you know what you're up against it takes some of the frustration out of the situation. So, I appologize in advance for explaining how lice grow and how this remedy works against lice. Also, through all of this, nobody else in the house got them even though my son, then age 4, and daughter shared a bed.
Last school year my daughter, then age 8, had lice. It took me from the end of Christmas break (when I found them) till about March. As soon as I found them, I went to the school to let the nurse know because my daughter said a couple of the other girls had been talking BEFORE Christmas break about the fact that their moms had just treated each of them for lice. I was told that the school couldn't do anything about the other girls because it's a privacy issue and "lice are only a nuisance, they arent't dangerous because they don't carry diseases" and that my daughter could not come back unless she had NO CRAWLING bugs. I had to fight the lice while the other girls kept coming to school with lice without being checked. It turned out several classes were dealing with this and the teachers could only send one student at a time IF they SAW them scratching. The nurses won't check everyone like they used to. Because the nurse now knew about my daughter, she would randomly call my daughter out of class and check for bugs. If she found any, she would call me to take my daughter home and lecture me AGAIN about how I needed to get this taken care of even though I was keeping her informed of which treatment I had tried the day before. It was like fighting an uphill battle. I actually started crying in her office IN FRONT of my girl because I was being talked to as if I wasn't doing anything!
I started keeping my daughter's hair in a braid EVERY day at school so it couldn't brush up against anyone else and pick up more OR give them to anyone else. While we were fighting this, the two girls (who STILL had lice) were closer than ever and told my daughter "oooh, since we all have lice it's okay that we touch heads", my daughter rounded on them and told them "after what I'm going through, keep your heads away from me! I don't want to get them again!"
First I researched everything I could on lice to find out what to use. I found every home remedy anyone can think of and tried a few.
I tried the different chemicals, short of going to the Dr for the prescription stuff. You are only supposed to use each chemical twice, about 1 week after the first treatment of that chemical. Using the chemicals more than twice runs the risk of the poison actually causing medical problems for your child, but it will not make the lice "pesticide resistant", that's just an urban legend.
Someone finally told me about the Robi electronic lice comb. You can find it at places like Walgreens for about $30 and it runs on batteries.
The way it works is this: it has a row of metal teeth that have an electronic current running through them. When it is turned on, it lets off a high-pitched buzzing sound. If two of the teeth touch a living creature (your bare finger, lice) then the buzzing stops until the finger or louse is removed. THE ROBI DOES NOT KILL THE LICE, it just finds them! It normally does not shock you, but sometimes there is ONE SINGLE spot on the head that will get a shock each time you do a comb-through. My daughter's spot was on the back of her head: she knew exactly when I was getting close and would remind me. Once you find this spot, just be careful around it. You start at the top of the head and SLOWLY comb down the hair, one section at a time, keeping the comb flush against the head (and neck and back for longer hair). The first time takes the longest.
You don't necessarily have to cut your child's hair. My daughter's hair was down to her waist and she has longish hairs on her neck as well, so the lice were actually crawling between her shoulder blades and biting her since the hair on her back was about 1/2 an inch long which is all they need. That's the reason for keeping the comb against the skin until you run out of hair.
As you go through the hair, the comb will pick up the lice and you'll know because the buzzing will stop. Slowly comb the rest of the way down that section. If you just pull the comb out, the lice will be pulled off and stay in the hair and you have to find them again. Once you get to the end of the hair, hold the comb over a white paper towel and, using the "brush" that comes with the Robi, brush the lice onto the towel. You can also do this into a bowl of water to keep them from crawling away (just make sure you don't get the Robi wet). I kept a magnifying glass with me so that I could make sure that I was actually getting the lice out of the comb. This comb will get everything except the eggs; well it will get a few eggs, but it's not made to get them. Do this every morning AND evening.
The lice hatch at all times of the day. The eggs MUST be no farther than 1/4 inch away from the scalp to have enough warmth to hatch. Once the hair grows and the egg gets about 1/2 an inch away from the scalp, the eggs will die without hatching. The bugs must feed within 18 hours or they will die, so if you bag stuff up it doesn't have to be for a whole week. And the spray stuff for your caouch and car is useless, but vacuuming and running stuff through the drier can work if the clothing can tolerate high or medium heat, not low. It takes one day, more or less, for each stage of developement for the lice (a couple of days for the egg stage, one day to go from one stage to the next of each larval stage). There are two larval stages: a very tiny clear one that looks like a tiny spider that is very hard to see and the pre-adult stage that is the same clear color as the previous one but shaped like the adult (long back-end and small body where the legs are attached). The adult is about 1/4 inch long, dark brown and can lay about 6 eggs a day. Once you have gone through the hair the first time and have gotten just about everything out, then you will still have eggs and sometimes a few bugs left. The first time we did it, it was at night and took quite a while (super long hair past her bottom). The next morning, it took a bit less time and only found 1st and 2nd stage larva. Over the next week or two all we found were the first stage larva because we weren't giving them the time to change to the next stage. After about two weeks, her hair had grown enough so that the eggs that were left were 1/2 an inch or more away from the scalp and couldn't hatch. Towards the end of that time, it only took about five minutes to go through her hair. I never had to cut her hair. Every now and again I still go through her hair. I don't know if your children have longish hair or not, but if you don't want to shave their heads, I recommend trying this.
Good Luck!