HEAD LICE
Oh the ever infamous head lice, just the thing to give you the heeby jeebies and leave you scratching your head for hours! If you have ever had it you know that aside from being itchy, it is embarrassing, annoying, very contagious and very hard to get rid of.
The head louse is a parasite that lives exclusively on the scalp of humans and chimpanzees (there are other types of lice that infest other mammals, but I'm not going to get into that). The head louse will only live on the scalp, and lice that live on other regions of the body, though distantly related, are different than the head louse and will not be discussed here. Lice feed off of the blood of humans, and since they cannot fly or walk, they cannot live any place but the human head, and are transferred through contact. Lice have legs that able to grab onto the hair shaft and move from hair to hair, so the most likely method of transference is through head to head contact, and less commonly (but not impossible) through shared brushes, hats, etc.
Lice lay eggs that are attached to the hair shaft. The egg requires heat, so in cooler climates the egg will be attached closer to the scalp, but in warmer environments they may be laid much further down the hair shaft, so it is incorrect to assume that if a nit(egg) is a few inches away from the scalp, it is dead. Live nits tend to be brownish, and hatched nits are white.
Lice can be very hard to treat. The insects have evolved and are more resistant to the treatments sold in the stores. Often, treatment needs to be repeated to be effective. Tea Tree oils and shampoos can be effective if used regularly. The most important thing is to used a nit comb (a small comb with very fine teeth that can be purchased at a drug store). You will need to go through the hair, in tiny sections, pulling the comb from root to tip and checking the comb after every pass through for nits or bugs, which you need to drown immediately. This procedure should be repeated daily until it turns up no lice or nits for at least two days. Pay special attention to the nape and behind the ears, as these areas tend to be warmer. It is a tedious job, but missing even one live nit or bug could lead to another infestation.
Dyeing or bleaching the hair is not an effective way of removing lice.
Lice prefer clean hair (since it is where they live an breed), so using hair products such as gel or hairspray can help make you an unfavourable host for a lice infestation. It is also important for parents to check their kids' hair as schools are not mandated to do lice checks any more.