Lice
It is not a pleasant subject but lice and nits can be very common with children, young and old. As a child I never had lice but I caught them at 21 and it was not a pleasant experience. I must not have gotten rid of them in the first place because they were back two weeks later.
There are some things that you can do. You can go the chemical way or the natural way. I tried three different types of chemical formulas. My friend, though, had success by leaving vegetable oil and a shower cap on her hair for several hours. the lice cannot hold on for such a long period of time.