Tea Tree Oil & Lice Treatment

The Centers for Disease Control and Prevention estimates that 6 to 12 million infestations of head lice occur each year in the United States. Over-the-counter and prescription medications can treat these pests, but they depend on chemical pesticides for success. Recently, interest has turned to tea tree oil as a less toxic alternative for head lice fumigation. If you decide to use tea tree oil for head lice removal, you should exercise caution. Some consumers have reported allergic skin reactions.

Considerations

Current over-the-counter shampoos for lice removal contain pyrethrin, a natural insecticide derived from chrysanthemums, and permethrin, a synthetic pesticide like pyrethrin. Prescription treatments contain malathion, an organophosphate, and lindane, an organochloride. These compounds kill the adult lice and must be reapplied 9 to 10 days later to kill the eggs that hatch after the first treatment. In some geographical areas, lice are resistant to over-the-counter medications. Also, the prescription shampoos can not be used on children, pregnant women or adults with compromised health.

Effect of Tea Tree Oil on Lice Behavior

According to Deon Canyon at James Cook University, Australia, tea tree oil was more effective as a lice repellent than peppermint oil and the synthetic repellent, N, N-diethyl-3-methylbenzamide (DEET). In this study, "A Comparison of Botanical and Synthetic Substances Commonly Used to Prevent Head Lice Infestation," published in "International Journal of Dermatology" in 2007, tea tree oil repelled 55 percent of the lice from a treated area. Lavender oil was effective at 34 percent repulsion, and DEET repelled 26 percent of the lice.

Tea tree oil also was more effective at stopping lice from blood feeding. Sixty percent of the lice treated with tea tree oil did not feed, whereas 40 percent of the lavender group did not feed. Treatment with essential oils was limited by the slipperiness of the infected hair because the lice could not get to the active ingredients.

None of the substances tested was completely effective for inhibiting lice from invading or feeding. The authors of this study suggest that if 55 percent of the lice fall off of the infection site, they will die from lack of food. Of the 45 per cent remaining, 60 percent will not be able to feed.

Effect of Tea Tree Oil on Lice Survival

In 2008, Australian researchers published a study in "Medical and Veterinary Entomology." In this report, "In Vitro Efficacy of Over-the-Counter Botanical Pediculicides Against the Head Louse Pediculius humanus var. capitis Based on a Stringent Standard for Mortality Assessment," they compared a 5 percent tea tree oil product with 1 percent permethrin, both commercial products available over-the-counter.

The tea tree oil product killed 98 percent of the lice after 30 minutes, but the permethrin product killed only 50 percent of the lice. Another product containing 10 per cent tea tree oil diluted with 1 per cent lavender oil killed 85 per cent of the lice in 30 minutes. This apparent discrepancy led the scientists to speculate that the viscosity of the 5 per cent tea tree oil might also play a role in the report of lethality.

Mechanism of Action

Acetylcholine is a neurotransmitter responsible for nerve transmission in muscles. If too much acetylcholine remains at the receiving nerve, the chemical signal for muscle contraction is continuous. The result is a muscle unable to relax.

Organophosphates are excellent pesticides because they inhibit acetylcholinesterase, an enzyme that destroys acetylcholine. This results in overstimulation of the nervous system and a breakdown of insect life processes. Research published in "Journal of Pharmacy and Pharmacology" in 2003 showed that tea tree oil inhibits acetylcholinesterase. This study was titled "Inhibition of Acetylcholinesterase by Tea Tree Oil."

Precautions

According to Medline Plus, most shampoos with 5 to 10 percent tea tree oil can be used for up to four weeks. Tea tree oil taken by mouth can cause abdominal pain, inflammation and other serious side effects. If you use tea tree oil for an extended period, there is a risk for allergic rash, blistering and itching. Tea tree oil has caused temporary hearing loss in animal models. Tea tree oil may also interact with other insect repellents and lice treatments.