Flexi Says: Head lice are obligate ectoparasites. These parasites live on the outside surface of other organisms and feed on blood from the skin. They are transmitted by direct contact with an infected person or with objects such as hair brushes, pillows, or clothing items that have lice or their eggs, which can live for several days off of a host. Other species of lice include pubic lice which are insect parasites that are transmitted sexually. They suck the blood of their host and irritate the skin in the pubic area.