Lice infestations are one of the most common communicable conditions suffered by children. Nevertheless, as unsanitary conditions are sometimes believed to promote lice, their appearance can quickly put sufferers (not to mention parents and school administrators) in a very hairy situation!
In fact, head lice are generally indifferent to environmental conditions beyond their natural territory, namely the scalp. (Most lice can't even survive for more than a day or so away from heat of the body.) In addition, lice can't fly or jump, so transmission most commonly occurs through direct bodily contact or through sharing of personal items such as combs, hats, sweaters, and towels.
Still, close quarters can certainly contribute to the spread of lice. In the World War I trenches, lice was rampant and soldiers cropped their hair short to try to avoid the “cooties” (a term thought to derive from the Malay word kutu, or biting parasite – though how the word traveled to the trenches is unknown.)
If you do discover a lice infestation, there are special shampoos, and even chemical treatments, that can be used to address it. Specialty fine-tooth combs can also help pick lice and nits (or lice eggs) from hair. Finally, bedding and clothes should be well cleaned – and perhaps even discarded. Worth remembering if you're feeling lousy!