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How long have lice been on my children's heads?

Head lice are parasitic insects that live on the scalp and although they do not transmit diseases, they are contagious, very annoying and sometimes difficult to get rid of. One of the questions you might ask is:

How long have lice been on my children's heads?

There are several ways to check how long you may have had lice.

It is important to know how long you have lice because the longer the child has lice the harder it will be to treat them. A prolonged and significant infestation may require more time to treat.

There are some signs to identify how long you have had lice:


Normally you don't feel itchy scalp once you get lice. You may not be itchy until 4 to 6 weeks after getting lice, this is because lice are slow to multiply and itch.

The itching is due to the skin's sensitivity to the saliva that lice release when feeding. If you've had lice before, you'll likely get symptoms more quickly because your body is already sensitized to lice saliva. In this case the itching may occur 2 days after the infestation.

Finding Lice and Nits

It is also possible that you do not have symptoms associated with lice, in which case it is necessary to identify them visually.

It can be difficult for someone with less experience to identify lice and easily think that dandruff and/or hair product residues are nits and vice versa. The best way is to run a fine anti-lice comb through your hair (from the root to the ends) if you find any nit-like residue and it doesn't come out easily, it could be the first indication that it's nits. Lice do not like light and are very small – two factors that make them difficult to identify. But there are ways to tell how long you've had them based on where and how you see them.

Lice infestation schedule:

  • Few nits: less than 2 weeks. An adult louse travels to the hair and starts laying about 6 to 10 nits a day, which take about 9 days to hatch. So if you look at your scalp and don't see visible adult lice and lots of small nits, chances are you got lice in the early stages and have had them for less than 2 weeks.

  • Nits and nymphs: 1.5 to 2 weeks. If you find nits and small, almost transparent lice moving around, you probably have lice at 1.5 to 2 weeks. This is because you don't find many adult lice, but small nymphs ("baby lice") hatched as well as far more nits than a person who caught lice just a few days ago.

  • Nits, nymphs and adult lice: 2 weeks or more. If you find lice of different sizes, you may have had lice for at least 2 weeks. If you have symptoms such as itching and a wide variety and number of lice, you probably have had lice for at least four to six weeks or possibly longer.

  • Nits more than 6 mm from the scalp: old infestation. You only see small nits more than a quarter of an inch away from the scalp, it's probably an old infestation and it's not active. He treated the lice and the nits (empty and inactive) are still "glued" to the hair strands and as it grows they move away from the root.

If you have any doubts, you can always visit the Happy Heads Clinic and we do a free diagnosis to check for lice and nits. Book now!

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