To treat head lice, the liquid should be applied to the scalp and rubbed into dry hair from the roots to the tips until all the hair is moistened. The best way to do this, particularly with with long hair, is to make a small parting and apply a few drops of the liquid along the hair, then spread this evenly along the length of the hair. Repeat the process with numerous other small sections until the whole scalp has been covered. Leave the hair to dry naturally in a warm but well ventilated room (don't use a hairdryer). After 12 hours, or the next day if preferred, shampoo the hair in the normal way. Rinse the hair and comb it using a fine toothed metal nit comb while the hair is still wet to remove the dead lice and eggs.