Pet and Head Lice Shampoos Linked to Autism

Two new studies links pesticides to childhood autism, according to a report in New Scientist.

The first study links autism to pet shampoos designed to kill fleas and ticks, and is described as "one of the first large-scale population-based studies to look at how environmental factors and their interactions with genes" trigger autism.

The insecticides in question are pyrethrins, and mothers of children with an autism spectrum disorder were twice as likely to have used a shampoo with pyrethrins while pregnant, particularly in the second trimester.

The second study suggests pregnant women exposed to organophosphates, another class of insecticides, were twice as likely to give birth to children with developmental disorders like autism. These pesticides are used in agriculture, as well as in head lice treatment, pet shampoos and other insecticides used in households.

Pesticides often kill by interfering with the nervous systems of insects, and some have been shown to damage the human nervous system, too. The search for a cause of autism has focused on environmental contaminants or chemicals that might interfere with the normal development of the brain.

The startling rise in autism diagnoses has focused attention on the hunt for the cause or causes of the disorder, but so far nothing has yielded an effective treatment or preventative regimen.

The scientists involved in the studies told New Scientist that the insecticides implicated are unlikely to be the only causes, and that they most likely prey on children whose genes make them predisposed to the disorder.

Regardless, the studies offer yet another cautionary tale about the use of toxic chemicals, particularly at home where children (and, importantly, pregnant women) are likely to come into contact with them. A rule of thumb: If it's strong enough to kill a stubborn bug, it could be strong enough to affect your health.

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