If this has happened to you then you can stop feeling like a terrible, neglectful parent who should have spotted the lice earlier. You've come up against one of the most successful parasites when it comes to man. Other parasites seem to have all but vanished from the lives of modern man as better personal hygiene has become widespread but head lice still thrive.

Unlike other parasites that have infested humans the fact that we now keep clean has no impact on Pediculus Humanus Capitis as head lice are scientifically known. Whether the hair is clean or dirty, head lice just don't seem to care. And washing the hair neither dislodges them nor drowns them.

Of course, as a good parent you're probably thinking you should have noticed your child had lice much earlier on but the fact is that nature has design head lice to be difficult to spot. They wouldn't have thrived for thousands of years if they could be seen with just a casual look. Their colouration, their size and the way they move through the hair are all designed to make them hard to spot. Unless you are actually looking for them you are unlikely to see them until the hair has become heavily infested.

As for the eggs, or nits as they are called, they are even more difficult to see and it can be very difficult to tell the difference between a nit and a flake of scalp skin if you've never seen a nit before.

So what about all the scratching that goes with head lice, surely you should have noticed that. Although frequent scratching of the scalp is an indication of lice only about a third of those infected will do this. The itching is caused by an allergic reaction to the bite, or more specifically the saliva produced during the bite.

It's thought that it takes several hundreds, if not thousands, of bites before the scalp of someone who is allergic to louse saliva will become itchy enough for them then to begin scratching. By this time the hair will already have a thriving colony of head lice living in it.

Because of all this it is good idea to have a routine of regular checks for head lice during the vulnerable school years when the chances of catching them are at their greatest. You only need to check the hair once or twice a month unless there are rumours of an outbreak when you'll want to do it at least once a week.

Get yourself a good head lice comb and work methodically through the hair inspecting the comb as you go. With a bit of practice you should be able to do this quite quickly. By carrying out regular checks you can prevent a lot of tears and embarrassment all round.