Believe it or not, what I regularly use on my daughters hair is nothing more than conditioner and a nit comb. The conditioner seems to loosen them off, makes them visible and also stops the comb damaging the hair. I then rinse it off when finished. I don't like to use all the chemicals, as my daughter is asthmatic, but find if done thoroughly it clears them away, plus the fact the conditioner is thoroughly combed through the hair makes it really shine.
Give it a go its less harmful to your child and as effective as any treatment I've used.