Just went through this and got rid of them in 4 days (with 12 more days of "after care". PLEASE do NOT use pesticides on your children. After researching about how harmful it can be, I would never do that again. The key is in the combing and meticulously going through the child's hair for at least 10 days from when you spot the lice. In addition to the metal comb to remove the eggs, while there were still live bugs, we killed them with the Robi Comb which zaps them dead. That item is amazing! After Robi Combing we washed her hair, left the conditioner in and combed the conditioner, dead bugs and eggs out with the metal lice comb. We did this every day.
Have you been combing daily with the lice comb to remove the eggs? Nothing kills the eggs and they will just keep hatching...they MUST be physically removed! You need to use a metal lice comb...the plastic ones stink. Ask your pharmacist if they have them. Also, when checking hair for eggs daily (in the SUNLIGHT--next to a window that gets good sun) you need to check very small (1/8 inch rows) sections of hair at a time, holding them straight up and looking at them from both sides in the sunlight. When I started doing this on the 3rd day, I had thought we were lice free with NO eggs & found 5 more eggs that first day doing it this way (but no more after that, even though I checked every other day in the sun to make sure). Remove them by cutting the whole strand off and flushing it down the toilet or combing the egg out and washing it down the sink. You should also get a good magnifying glass (in walmart by magnifying eye glasses near pharmacy). Another helpful tool is at least 6 big metal hair clips like hairdressers use for sectioning off the hair as you do each section. Then go through one section at a time in very narrow rows.
Drying the pillows, pillowcases and sheets every morning for those 10-15 days is very important (30 minutes per load on high heat-don't overstuff dryer). Also, I make my daughter keep her coat in her backpack at school, then she leaves the backpack in the car and brings the coat in to go straight into the dryer for 30 minutes. We braid her hair every morning and use Fairy tales lice repellent products (liceguard repellent works well too) on her hair every morning. I also wash her hair a teatree oil and mint shampoo by Organix (at walmart & Suave Coconut conditioner with a couple drops of real teatree oil added to the bottle. I never want those critters back!!
The olive oil or mayo treatments are extremely messy, leaking out of the cap, for a child, IMO and frankly unnecessary if you do all the rest above.
I put together a list for our school's nurse to hand out with more do's and don'ts for lice (she was completely clueless and no help). If you message me, I will send it to you...this is a LOT of work, but I say better a LOT of work for 14 days than having lice over and over for 6 mos and spreading them to others!