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Last updated January 1, 2014

Common Insecticide Ingredient May Cause Allergic Reactions

Charnicia E. Huggins, Reuters, August 2000

NEW YORK (Reuters Health) - While household insecticides may be effective at getting rid of pesky little creatures, certain ingredients such as pyrethrin may trigger allergic reactions including acute asthma attacks in humans, according to one case report.

An 11-year-old girl with a 5-year history of asthma gave her dog a bath using a shampoo that contained 0.2% pyrethrin. Within 10 minutes, she developed severe shortness of breath with wheezing and was immediately taken to the hospital. Despite aggressive treatment by healthcare workers, she died of respiratory arrest less than 3 hours after her exposure to the shampoo.

The researchers note that the pyrethrin shampoo appeared to be the trigger for the girl's asthma attack because the dog had been in the family home for several years, and the girl had suffered a mild asthma attack when she was exposed to the shampoo two years previously.

Pyrethrin is an insecticide ingredient prepared from pyrethrum flowers, "plants of the Compositae family, which includes daisies and chrysanthemums," notes Dr. Sheldon L. Wagner in a letter published in the August issue of the Western Journal of Medicine. It has a low toxicity in humans, but it can cause skin rash, upper respiratory tract irritation, and, in rare cases, potentially life-threatening asthma attacks, according to published reports.

Yet pyrethrin is not "currently classified as (an allergen) by the Environmental Protection Agency," Wagner writes. Due to the extraction process of pyrethrin from pyrethrum, pyrethrin "may contain small, but still allergenic, amounts of the impurities found in (pyrethrum)," he explains.

Pyrethrum is still being marketed as an insecticide and it is a known allergen, but the label does not warn the public or physicians of this fact, Wagner told Reuters Health.

Wagner suspects that pyrethrin may also cause allergies. This may be a cause for concern because of its increasingly frequent use in homes and its easy accessibility by the public, he cautions. "Manufacturers are not required by the Environmental Protection Agency to state on the label that the pyrethrum formulations are allergens," he adds.

In light of the circumstances surrounding the 11-year-old girl's death, healthcare professionals faced with respiratory illness or skin allergies of an unknown cause should consider the "possibility of an acute allergic reaction occurring from the use of any currently marketed pyrethrum insecticide," Wagner advises.

"This case suggests that physicians should also be alert to formulations marketed as pyrethrin," Wagner stresses.

Furthermore, consumers who use pyrethrum or pyrethrin insecticides "should be aware...of the possibility of an allergic reaction the same way if they knew they were allergic to poison ivy or poison oak or ragweed," Wagner stated in an interview.

Pyrethrin is currently under consideration for re-registration by the Environmental Protection Agency (EPA)--a process that will be concluded by 2002, according to an EPA spokesperson. The EPA's re-registration program "ensures that older pesticides meet contemporary health and safety standards and product labeling requirements, and that their risks are mitigated."

Source: Western Journal of Medicine 2000;173:86-87.

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