Concerns on the Use of Animal Products to Treat Head Lice

Date: September 12 2013
From: Leo Schep, National Poisons Centre, Otago University
Subject: Concerns on the Ongoing Use of Animal Products to Treat Head lice in Humans

The National Poisons Centre (NPC) is concerned about the use of animal remedies to treat head lice. Of note are those products containing the organophosphate fenthion. In the last 10 years, for example 26% of calls to the NPC on these products were as a result of using them for head lice treatment, particularly for children.

Organophosphates are widely used as agricultural insecticides and as household pest control agents. Organophosphates are highly toxic and may be absorbed through the skin. In very low concentrations some less toxic organophosphates, predominantly malathion, have been approved for human use to control head lice. Given the higher concentration of fenthion in animal remedy products, typically 20% concentration, and its greater toxicity when compared to malathion, it is estimated those animal products containing fenthion can be considered as 140 times more toxic than those approved for human use.

Symptoms can be most severe and rapid in onset (within a few minutes to an hour) with ingestion. Skin absorption is less rapid, so that with a predominantly dermal exposure, symptoms may be delayed for up to several hours.

Mild to moderate signs and symptoms following a toxic exposure to these agents can include increased secretions of saliva, tears, and mucus, predominantly from the lungs. Also, patients may suffer vomiting and sweating and fluid bowel motions. The intensity of symptoms will depend on the toxicity and concentration of the organophosphate, and duration of exposure. Using these animal remedies for prolonged periods of time, typically when applied to the scalp, increases the risk of toxicity, even via the dermal route.

The NPC discourages such practices and if users suffer symptoms following such an exposure, they must seek prompt medical attention. Only head lice treatment products approved for human use must be used.

Dr Wayne Temple, Director National Poisons Centre;
Dr Leo Schep. Toxicologist, National Poisons Centre
Mr Robin Slaughter, Poison Information Officer, National Poisons Centre

ENDS

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