Tea Tree Oil for Lice (And Many Other Things)?

Alana wrote in:

My boy/girl twins will be 3 in December, and have just begun nursery school. It seems like reports of head lice are everywhere these days, and adding tea tree oil to shampoo (or using it as a spray on the hair) seems to be a popular recommendation for prevention. I thought that might be worth trying, thinking the worst thing that could happen is that it wouldn’t do anything and I’d be out a few bucks. But I did a little Googling, and it looks like there are some studies linking the use of tea tree oil to gynecomastia in boys.

Tea tree oil is one of those “natural” things that sounds like it has a use for everything, but I’m wondering if you know of any evidence that would suggest it should or shouldn’t be used? And if not, any other suggestions on lice prevention?

As Alana says, tea tree oil is indeed one of those things that seems to have use for almost everything—or at least that’s what you can find on Google. I quickly found sites suggesting it be used to freshening carpets, cleaning cuts and scrapes, treating fleas on your dog, making your breath fresh, taming asthma, and treating almost any skin condition from psoriasis to insect bites to body odor. And lice, too—preventing and treating lice both on you and your dog, apparently (yes, dogs can get lice, but not the same lice as humans. Lice are persnickety about whom they infest.)

Can one magic potion do all of that?

Tea tree oil is extracted from the leaves of the Melaleuca plant from Australia. It’s sometimes called a “tea tree”, but it’s a different plant from the one that drinking tea comes from. There’s also tea oil out there, which is meant for seasoning and cooking—that’s different stuff, too. Tea tree oil has become especially popular as one of many so-called “essential oils” often sold via multilevel marketing schemes. That term itself, essential oil, seems to be rooted in the alchemy of the middle ages, though it’s been newly popularized as a catch all for oil-based essences of plant fragrances and other compounds.

The best reference I could find summarizing what’s known about tea tree oil comes from the US National Library of Medicine’s Medline Plus database.  Some studies have shown it’s possibly effective when used topically for athlete’s foot, toenail fungus, and acne. There’s insufficient evidence to make a reasonable judgement about its use in any other health conditions.

For lice specifically, I looked through the Medline database for all relevant studies. There are a few, but the results aren’t really impressive. A 2007 study looked at tea tree oil along with other botanical and synthetic substances to prevent lice—including DEET, a commonly used insect repellant. Though tea tree oil did repel lice, it was only to a small degree, and the authors concluded that none of the tested products were effective at preventing lice.

In 2011, a blinded and randomized trial took hair clippings with attached lice eggs, exposing them to different essential oils (tea tree, lavender, eucalyptus) versus a standard “suffocation” type of product. Rounding off, the suffocation chemical killed 70% of eggs, and tea tree oil 45% — not great, though better than nothing.

A more-promising study from 2012 combined tea tree oil with the chemical nerolidol, and found good effectiveness against both lice and their eggs, at least in a laboratory setting (tea tree oil alone wasn’t as effective, especially against unhatched eggs.)

Net: no chemical treatment, whether based on botanical essential oils or any other chemical, seems effective at preventing lice. There’s some promise that tea tree oil might be part of a treatment regimen, but at least so far synthetic “traditional” lice treatment strategies are far more effective.

Tea tree oil is generally safe when used topically, other than occasional local irritation or a local allergic reaction. There was a report that continuous, high-surface-area skin exposure could cause estrogen-like effects (specifically, gynecomastia, the growth of breast tissue in boys), though it’s unlikely that short-term, limited use of this product would cause the same effect. Tea tree oil is poisonous and should not be ingested or used near the mouth.

Alana asked about preventing lice. What can work is trying to discourage children from wrestling, playing close, or sharing hair accessories. If lice do appear, stay cool. Remember that even though they’re icky, human lice do not spread any disease and are not a sign that your children are unclean or uncared for. There are a number of OTC and prescription products that can effectively kill lice (be sure to follow the directions, and repeat the process as directed.) Intense efforts to rid your child’s bed or your entire house are not necessary—the only lice that spread from child to child are the ones on heads. Lice that fall off are dead or dying, and are not spreading to other people.

More lice news: a 2014 study found that at least some louse eggs hatch as late as 13 days after they’re laid—which means that repeating lice treatment in 7-10 days may be inadequate (that is, it may leave some viable eggs ready to hatch.) Since most lice treatments don’t effectively kill the eggs, the timing of re-treatment needs to be both early enough so that newly hatched lice aren’t mature enough to lay new eggs, but late enough so that all eggs have hatched. If this 2014 report is correct, the best strategy may be to repeat the lice treatment twice—at 8 days and again at 15 days. It’s more complicated, but would effectively knock out all lice and eggs. Of course, no strategy will overcome the potential that your child will get lice back from another child at school—but, again, they’re still just lice, and we need to keep that in perspective. Itchy, yes. Icky, sure. But really, still, not something to get too worried about.


This blog was originally posted on The Pediatric Insider.

© 2015 Roy Benaroch, MD