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An electron microscope image of a head louse viewed through magnifying glasses. ((Frank Gunn/Canadian Press))

Medical experts say head lice are not a health risk but many Canadian schools continue to screen students for the pests and send kids home if they have them.

"The difficulty with head lice is that it creates so much unnecessary panic," said Dr. Shirley Blaichman of the Canadian Pediatric Society in Montreal. "Head lice are a nuisance, but they're not a medical problem."

The six legged, blood-sucking insects live on the scalps of humans, where they eat and multiply.

Twice a year, a school in Barrie, Ont., hires a company to check its students. If any lice are found, the student is immediately pulled out of class.

The policy at most school boards CBC News checked with requires students with lice to leave school and stay home until the infestation is cleared. The main reason for keeping the policies in place appears to be "ick" factor of the pests.

Lice are notoriously difficult to get rid of. Over the years, people have resorted to kerosene and mayonnaise as home remedies, as well as medicinal shampoos.

At a centre for treating head lice, one woman who was there with her daughter said they have had dozens of infestations over the years.

"Frustrating to the point that you want to cry," the mother said. "You just don't feel like you're ever going to get rid of it."

Yet both the mother and daughter back the school policies, even though experts say there is no medical rationale.