I assume you mean head lice (nits is the term used for the eggs)
I found this info:
''Head lice are usually just a nuisance. But, occasionally, their bites can become infected. This is more likely to happen if you scratch your head and pull off the scabs. If the lice in your hair are carrying bacteria (germs), these can get into the wound.
One of the most common infections from head lice is impetigo of the scalp. This is a skin infection that lice can spread from one person to another. Impetigo causes crusty, itchy scabs and needs to be treated with antibiotics. Impetigo is also easily passed on (highly contagious). If you have crusty or itchy scabs on your head, you should see your doctor straight away. You should get rid of the head lice while you're taking antibiotics for the infection.
Other symptoms
If head lice go untreated for a long time (for example, 12 to 18 months), they can make you feel generally low and tired.3 5 This is because your immune system becomes worn down after that long''
I can't imagine leaving them untreated...the itching must be tremendous. I caught just the one from my daughter and that was almost unbearable!