What happens if you have head lice and you can't get them all out because a lot of them have spreaded too much, then?

Call your doctor: Lice can be hard to eradicate because they can become resistant to medications available at the grocery store. Discuss with your doctor- there are prescription options. Consider cutting your hair short which can make it easier to remove the insects and eggs. Have someone help you - you need a fine tooth comb and patience to remove all the eggs and insects from every area of scalp. Repeat often.