Lice can only survive for two to three days when off of the human body. Nits are eggs from the adult lice and are whitish and are firmly attached to hairs. The eggs hatch in 6-10 days and it then takes another two to three weeks for the lice to mature and be able to reproduce. Although many schools and day care centers have no nit policies, just because you have nits doesn't mean that you will have a lice infestation. Even after nits hatch, the casing can stay on the hair for a long time and it is hard to tell the difference between a nit with a live louse embryo in it, which can be infectious, and an empty one.
Nits are more likely to contain a live embryo if they are close to the scalp.
First, do a thorough check of your child's hair and scalp to look for live lice. If you don't see any, then you may be able to just try and remove the nits on a regular basis and continue to look for live lice. Since most of the anti-lice medications are not ovicidal, meaning they don't kill the eggs, treating a child with just nits may not be necessary. If you find lice and nits on your child, use an anti-lice shampoo, such as Nix or Rid , and follow the package directions carefully. In general, you should apply it to washed and dried hair and apply the shampoo until the hair and scalp is saturated and thoroughly wet.