Treated lice on a child but she says it still itches, but i do not see anything?

Head lice: Itching may continue even after all lice are destroyed. This happens because of a lingering allergic reaction to their bites. Over-the-counter cortisone (corticosteroid) creams or calamine lotion may help. For severe itching, antihistamine medicines (such as benadryl) or stronger, prescription-strength corticosteroid creams may be needed. Don't give antihistamines without doctors permission.

Reaction: As long as you no longer see lice or nits you have treated sufficiently. Often there is a hypersensitivity reaction, ie. A lingering effect from the infestation which could explain the itching. This may last for upwards of a few weeks. Make sure to check behind ears, nape of neck to ensure complete treatment though.