Lice – which lay eggs, known as nits – are parasitic insects that are found on the head, eyebrows or eyelashes, according to the NHS.
The insects feed on human blood several times a day.
While they’re most common in children, adults are also at risk of an infestation.
But, how can the insects be spread from person to person?
“Head lice move by crawling; they cannot hop or fly,” said the Centers for Disease Control and Prevention (CDC).
“Head lice are spread by direct contact with the hair of an infested person.
“Anyone who comes in head-to-head contact with someone who already has head lice is at greatest risk.”
While head-to-head contact is the most common form of transmission, head lice can be spread without touching an infected person’s hair.
Head lice that are caught in combs can be spread from person to person, according to the National Institute for Health and Care Excellence.
It’s uncommon for lice to passed by sharing combs, but they can get caught in combs or brushes, and remain clinging to stray hairs in them.
They can then be returned to the head unhurt at a subsequent stroke.
Lice may also be spread in a swimming pool. They can survive underwater for several hours.
“Head lice have been seen to hold tightly to human hair and not let go when submerged under water,” said the CDC.
“Chlorine levels found in pool water do not kill head lice.”
The only way to be sure someone has head lice is by finding live lice, or nits.
Medicated lotions and sprays may help to kill head lice in all types of hair. You can buy them from supermarkets or pharmacies.