A Lousy, Nit-Picking Epidemic

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The school had been invaded, and officials were banning brushes and putting coats in plastic bags to seal off the points of attack. Five nurses worked all morning on the heads of 600 children at the Rachel Carson Elementary School in Gaithersburg, Md., spending five to seven minutes per scalp, looking for signs of infestation. In the end, 12% of the students and 10% of the staff were sent home. It was the worst invasion of head lice in a long time. "In other years we have two, sometimes four cases of lice," says Laura Hart Silkwood, the principal. "This is highly, highly unusual. The numbers kept rising."

And not just in Gaithersburg. Pediculus humanus capitis, the human head louse, is back in alarming numbers in school systems from New York to California. The epidemic had nearly been stemmed decades ago by a generation of chemical shampoos and rinses, but now the insect appears to be backed by a force more powerful than any shampoo: evolution.

Thousands of parents and school officials are calling county health offices to report that the standard arsenal of commercial lice-killing products seems to be having little effect. In Iowa, Virginia and Oklahoma, newspaper articles have discussed the merits of such home remedies as olive oil and vinegar. In Rhode Island, Idaho and Florida, parents are trading tips on smearing their kids' hair with vaseline, steam cleaning the carpets and storing teddy bears in the refrigerator. "It's creating a lot of havoc," says Wayne Kramer, the Nebraska state medical entomologist, who has received 125 calls since the beginning of the school year, many more than usual. "I think it's on the brink of being out of control."

The human head louse has been around for millenniums. Archaeologists have found evidence of head lice in the hair of ancient Egyptian mummies. And each year, 10 million to 12 million Americans receive unsolicited calls from the sesame seed-size insects, which set up shop in human scalps and lay eggs, or nits, that they cement to hair shafts. Head lice do not carry disease, but they are tenacious and a rather nasty sight. In the past few decades, the problem had been controlled with shampoos or soaps, many of them containing permethrin, the most widely used of the lice-killing chemicals called synthetic pyrethroids. In recent years, however, the frequency of infestations has increased, and ever greater numbers of children are becoming reinfested within days of treatment. All this has led health officials and researchers to begin worrying about the emergence of a resistant strain of the insect, impervious to permethrin.