As far as parasites go, they're not so bad, but there's no question that lice are a real nuisance. They live in human hair; indeed, they are so adapted that they can only live in human hair. They eat a diet of human blood, which they suck out of the scalp. They apply a strong adhesive to hairs and affix their eggs to them, so that they cannot fall off. Bites from lice are often itchy and raw. Once a person's hair is infested with lice, it's difficult to get rid of them. (As an aside: having lice is not a sign of poor hygeine. Lice actually prefer to live in clean hair.)
Lice are passed from head to head by close contact. The bugs jump from one head to another, and proceed to set up shop on the new head. Children are at the highest risk, for the simple reason that they spend the most time in close physical play with one another. As such, lice are a constant headache (no pun intended) in schools, where most of the transmission occurs.
The most effective way to get rid of lice is also the most onerous and time-consuming: you need to get a very, very fine steel comb and brush them out. It might take a half an hour a night of preening for two to three weeks to completely eliminate the lice and their eggs. In a culture obsessed with speed and convenience, it was only a matter of time before someone came up with a faster alternative.
Enter over the counter lice treatment. Wash hair. Apply treatment. Leave to sit on hair for recommended time. Rinse. Reapply if necessary. Ah, convencience!
The one tiny problem is the active ingredient in most lice treatments, a chemical called lindane. Lice are pests; lindane is a pesticide. More specific, it is an organochlorine, a potent neurotoxin that disrupts the endocrine system and affects the central nervous system. It has been in circulation since the 1940s, so long term health effects have been studied extensively. It can cause dizziness, headaches, nausea and vomiting, convulsions, tremors, muscle weakness, diarrhea, blood disorders including aplastic anemia and cyanosis circulatory collapse, cancers, and congenital birth defects. Children are at highest risk from lindane exposure because their brains, nervous systems and hormonal systems are still developing, and because children's skin is more permeable than that of adults. Lindane is also fat soluble, which means that it bioaccumulates (increases in concentration as it moves up the food chain).
So what are we asked to do with this known toxin? We are asked to rub it into the scalps of our children and leave it on while it kills the bugs. This is just about the best example I can imagine of the cure being worse than the disease!
As a final insult, lindane is only about 80% effective in killing lice. The 20% of lice that survive lindane applications reproduce and pass on their lindane resistance to their offspring. Therefore, not only is this pesticide very harmful, it is also ineffective. After decades of studiously applying lindane to chidren's heads (if anything, parents are inclined to leave the treatment on for longer than the recommended time, further exposing children to danger), lice are a worse nuisance than ever.
All of which brings us back to the tedious job of preening our children's hair. I guess we're not so far evolved from our primate relations after all. But think of it this way: maybe it will force parents to spend a little time with their children...
See also: Cosmetic Pesticides.
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