Head lice are small wingless insects that live on human head or hair. They are common, particularly in children. They are very well adapted to grasp human hair shaft. They cannot fly, jump or swim and are spread by head to head contact.

Head lice feed on human blood, several times a day. A head lice infestation is not the result of dirty hair or poor hygiene and it can effects all types of hair irrespective of its condition or length. Head lice effects only humans and cannot be passed on to animals.

Female head louse lays eggs close to the scalp on the hair shaft. Eggs hatch after 5-7days leaving empty egg shells (nits) glued to the hair shaft. These eggshells are more noticeable as hair grows and carry them away from the scalp.

Nymphs that emerge from egg shells take 7-8 days to grow to adult sized lice. They may take another 7 days to start breeding and hence it is important to remove them to stop them spreading.

Do head lice cause illness or disease?

Head lice do not transmit disease causing micro-organisms. However, they can cause irritation, resulting in itchiness. Sometimes, itchiness and subsequent scratching of the scalp can increase the risk of secondary infection.

Using insecticides and other substances to control head lice can actually have more serious health effects than the lice themselves. Swapping between different treatments or using several different treatments at the same time can cause serious skin irritation, itchiness and other complications. Registered chemicals that kill lice are usually safe, but excessive use of other substances, such as home remedies and other insecticides, can cause irritation.

How do you catch head lice?

Head lice cannot jump or fly from person to person. They are usually spread by head to head contact. Primary school-aged children, particularly girls are at greatest risk of exposure to head lice.

Studies show that lice are rarely transferred through clothing, hats, furniture or bedding. Lice or eggs may be attached to strands of hair left on pillows, bedding or furniture, but this is uncommon​​​

Page Updated: Tuesday 5 February 2013
Contact page owner: Environmental Health