Nits are blood-sucking parasites that live in human hair.
They are easily spread, and can be difficult to remove.
“Head lice are usually visible in the hair and on the scalp, especially during brushing,” said Great Ormond Street Hospital for Children (GOSH).
“The eggs are white in colour and can be found near the scalp.
“Head lice can reproduce and mature very quickly, so a few can quickly grow in number over a very short period of time.”
These are the most common signs of infestation.
Head lice feed on human blood to survive, and bite into the scalp.
Their saliva and faeces make the scalp itch, said the British Association of Dermatologists (BAD).
Some people may not experience itchiness, but could still be infected, it warned.
Finding live head lice on the scalp
The best way to find out if you’re infected with head lice is to look directly into the scalp.
Often, patients can physically see the lice in their hair.
“Female lice live for up to 40 days, during which time they can lay more than 100 eggs,” said the BAD.
“They attach their eggs to hairs close to the scalp surface. The eggs are yellow or white, and the size of a pin head.
“They take seven to 10 days to hatch, and the new lice can then lay more eggs after about seven days.”
Head lice can create a tickling sensation on the scalp of patients.
The feeling can make it difficult to get to sleep.
Difficulty sleeping can lead to irritability, so feeling bad-tempered may be a sign of an infestation.
An Infestation can make many people scratch their scalps raw.
On occasions, the scratching can leave visible marks and bumps on the scalp, neck and shoulders.
“There might be tiny red spots on the scalp,” said GOSH.
“It can take several treatments to get rid off the eggs and lice completely.
“Medicated shampoos and lotions contain quite strong chemicals, so some people may have an allergic reaction to them.”