What are head-lice?
Head lice are parasites which live on the hair and scalp causing itchiness and irritation. Human hair provides the ideal environment in which head lice can reproduce. During their forty day lifespan they can produce between 150 and 200 eggs which are laid about 2mm from the scalp where they stick securely to the hair. The eggs hatch approximately nine days later by which time the hair will have grown by another 2mm. Any eggs which appear more than 4mm from the scalp are therefore likely to be empty or dead.
