I know that the news today can be overwhelming, even just mentioning the word facts can trigger all sorts of reactions.
I’m Dr. Michael Greger and I happen to really like facts! So, I’ve devoted my life to learning all there is to know about the latest nutrition research, so that you and your family can lead healthier, more productive lives.
Today, we discover the benefits of an oil that comes from the leaves of the Melaleuca alternifolia tree – or tea tree, for short. Now you can’t make tea from tea tree oil –it’s actually poisonous to drink. But, you can put it to work on your skin and in your house.
Household cleaning products can be hazardous, landing hundreds of thousands of children in U.S. emergency rooms. And, “[t]he product most-commonly associated with injury [is] bleach,” which can be toxic even if used as directed.
We’ve known that those with asthma who work with cleaning products day in and day out can suffer adverse respiratory effects, a worsening of symptoms, “decline in…lung function,” inflamed airways. But, even cleaning workers without asthma can be affected. Even below so-called acceptable exposure levels, cleaners with or without reactive airways can suffer a substantial decrease in lung function.
Okay, but that’s people who clean for a living. “Although [we’ve known] that occupational use of bleach may have adverse respiratory health effects, it [was] unknown whether common domestic use of bleach” in the household may put lungs at risk—until now.
“Bleach use was significantly associated with [nearly five times the odds of] non-allergic adult-onset asthma,” as well as ongoing lower respiratory symptoms, such as chronic cough. The way bleach works is as such a strong pro-oxidant that – the thought is that it can lead to leaky lungs, and allow allergens to penetrate.
This phenomenon of cleaning product-induced asthma has been known for decades. More than three-quarters of the dozens of population studies looking into it have found “increased risk of asthma” or nasal inflammation. Ideally,…safer [cleaning products] should be available.” Unfortunately, this body of evidence has been largely ignored by the manufacturers and commercial cleaning companies. And, most of the workers put at risk are women. In fact, that may help explain some of the “gender differences in asthma.” “The relatively high frequency of bleach use for home-cleaning by women…around the world, together with the strong association between bleach use and non-allergic asthma…, emphasize the need for (re)-considering the use of bleach for cleaning…”
There are natural, environmentally friendly cleaning products that may offer a safer alternative. Safer, perhaps, but are they as effective? We didn’t know—until now. “The effectiveness of three home products in cleaning and disinfection of Staphylococcus aureus [the bacteria that causes staph infections] and [E. coli ] on home environmental surfaces.” “The first report [ever] of [the] performance of purportedly safer alternatives.”
“In the home setting, some individuals will select conventional products, such as bleach, due to familiarity;” it’s a smell “some…associate with cleanliness.” “Others are seeking less hazardous and environmentally preferable…‘green,’ ‘organic,’ or ‘natural’” disinfectants, which you can buy or make yourself—so-called DIY (do-it-yourself) recipes, that typically involve ingredients like vinegar, club soda, and plant essential oils, such as tea tree oil, prized for its antimicrobial qualities.
So, researchers pitted head-to-head Clorox bleach versus a natural disinfectant based on thymol, which is from thyme essential oil, versus a DIY recipe of half club soda, half white vinegar, with a few drops of tea tree oil. You could probably buy the bleach for around $3, the natural stuff for more like $7, but the DIY mix for less than a dollar. Yeah, but does it work?
On the bottle, it says bleach can kill 99.9% of germs, which is the EPA standard for the disinfection of surfaces that don’t come into contact with food, like the bathroom sink or something. They claim 99.9% of germs, but when put to the test, the bleach actually killed 99.9999% of germs, completely wiping out the E. coli and Staph germs, which even exceeds the EPA standard for food contact surfaces, like the kitchen counter. And, so did the expensive natural stuff—worked just as well as the bleach. But, the club soda/vinegar/tea tree oil concoction… flopped, allowing as many as a few percent of the Staph bugs to thrive.
Now, maybe they didn’t use enough of the tea tree oil, only adding about a drop per cup. But, from a performance perspective, “the [environmentally preferable] product is an effective alternative to…conventional bleach”—and, I would say, even better, since bleach is “well known as a respiratory irritant.” And, it’s “corrosive” too, and may end up damaging surfaces. What I would find interesting is to test how effective a cheap DIY thyme-oil solution would be.
In our next story we discover whether the effects of tea tree oil are anti-fungal or merely anti-inflammatory?
Our entire understanding of the cause of dandruff shifted with a landmark article published in 1984. Instead of relying on secondary sources, reviews, editorials, and opinion pieces, he looked at the primary literature, the original studies, and “was amazed to find out how overwhelming was the evidence of the [true cause], and how it had been ignored because it was so well buried under the mountain of error” since some expert in the 1800s put forth some bogus theory.
We now know that dandruff is triggered by a fungus that lives and feeds on the human scalp—the two major implications being, first, how “alarming” it is that some bogus theory can remain in the medical literature unchallenged for a century despite evidence to the contrary; and, second, hey, if it’s a fungus, what about trying tea tree oil, which contains components that have “antifungal activity” against a range of fungi.
That was based on studies like this, though, where tea tree oil in a Petri dish can fight off pathogenic skin fungi. But, you don’t know if it works for dandruff, until you put it to the test. A hundred and twenty-six men and women randomized to daily use of a “5% tea tree oil shampoo or placebo” for a month. The placebo worked a little bit, decreasing dandruff severity by about 10%, but the tea tree oil shampoo worked better—about a 40% drop.
“[O]nly one patient [in the tea tree oil group] actually achieved a complete response,” though one in the placebo group did as well. Thus, it seems that the “tea tree oil shampoo would require ongoing application for control of dandruff.”
Speaking of fungus, what about tea tree oil in the treatment of athlete’s foot? That may actually be our most common fungal skin infection, affecting up to one in ten. So, about a hundred patients randomized into one of three groups, a 10% tea tree oil cream, Tinactin (an antifungal drug), or a placebo cream. A month later, the fungus was wiped out in 85% of the drug group, but only about a quarter of the placebo and tea tree oil groups. This is somewhat surprising, since tea tree oil can kill off a fungus in a Petri dish—but, apparently, not on toes.
That reminds me of some of the oral health data on tea tree oil. It can wipe out some oral pathogens in a Petri dish, but have people swish a tea tree oil solution around in their mouth? So, if tea tree oil doesn’t influence the amount of plaque, presumably it wouldn’t help with gingivitis, the gum inflammation that’s caused by plaque buildup. But, no; here’s the twist. True, no reduction in plaque with a 2.5% tea tree oil gel—yet “significant reduction” in gingivitis scores. Since decreased gum inflammation occurred without a decrease in plaque, it appeared to just be helping more from an anti-inflammatory rather than antimicrobial mechanism.
So, “[t]his may be the basis for the popular use of tea tree oil in the treatment of [athlete’s foot].” But, people should realize it’s just symptomatic relief, and they’re not necessarily eliminating the underlying cause. Of course, maybe they didn’t use a strong enough concentration.
And, indeed, if you go with not a 10% cream, but up to 25 or 50%, you can get “mycological cure rate[s]” above that of placebo, but still not as good as the drug. And, at those high concentrations, some of the patients applying tea tree oil “developed moderate to severe dermatitis”—they broke out in a rash. But, hey, if you have a patient that doesn’t want to use the medicated creams, then a 25% tea tree oil application has a decent chance of knocking it out without being too risky. But, the standard over-the-counter antifungal creams may work better.
In our last story, tea tree essential oil is pitted against the antifungal cream Lotrimin for the treatment of fungal nail infection, but what about treating the underlying cause?
“Onychomycosis is a fungal infection” of our nails—usually toenails, but sometimes fingernails—characterized by nail discoloration, deformity, detachment, “thickening, crumbling, ridging. Reported prevalence is estimated to be about 1 in 25 people, though “it is more common in older individuals;” one in five over 60, and like half of 70-year-olds. Unfortunately, it’s really hard to treat, because the fungus can hide deep inside the nail, protected from the blood supply on one side, or anything you want to put on topically on the other. So, “recurrence after treatment is common due to residual [fungus],” even if you are able to beat it back. Many of the oral systemic treatments can be toxic, and “many topical [applications] require long treatment courses, which may limit patient compliance”—especially in patients who want to use nail polish or something to cover it up.
So, given all the problems with a lot of the prescription antifungals, “there has been a renewed interest in natural remedies.” Well, if tea tree oil can affect athlete’s foot and dandruff fungus, what about nail fungus?
Well, there was one head-to-head study comparing tea tree oil with a common antifungal drug; a double-blind, randomized controlled trial. “…Twice-daily application” of either the drug or pure tea tree oil on the nail “for 6 months.” Debridement was performed every few months, where some of the fungal mass is debulked, scraped, ground off. And, after six months, the drug only wiped the fungus out completely in about one in 10 cases, but looked better, with partial or full resolution of the appearance, in the majority of patients, either from the doctor’s assessment or the patient’s. And, the tea tree oil did just as well.
“The two preparations were comparable in efficacy of cure, clinical assessment, and subjective improvement”—even their cost was comparable. So, “[f]or patients desiring a ‘natural’ treatment for [athlete’s foot or nail fungus], topical tea tree oil is a reasonable alternative to prescription or over-the-counter antifungals.”
Speaking of natural treatments, how about a truly natural treatment? “One potential reason for the poor long-term benefits of any therapy [for nail fungus] is that it may be treating only a manifestation of underlying disease, such as generalized immune suppression or peripheral micro- or macrovascular disease.” Maybe fungal nail infections are just a manifestation of poor peripheral blood circulation that would normally allow your body’s natural defenses to keep the fungus from taking root in the first place. Evidently, there was a non-English language study of 400 patients that looked at the “relationship between blood circulation of the skin and the development of fungus disease”—that was the title—and “found a greater than 50% reduction in blood flow in patients with [athlete’s foot and nail fungus]…compared with patients without these disorders.” So, if fungal nail infections are “just a symptom of an underlying process, then treatment aimed at eradication of a pathogen may be unrealistic.” No wonder it just grows right back. “A more appropriate goal,” then, may be to just give up and live with it. But wait! If it’s a circulation problem, why not, instead, improve the circulation?
We’ve known since the 1950’s that you can effectively switch peripheral artery circulation on and off, like a light switch, within days by switching people between a low-fat plant-based diet and the more conventional diet that contributed to the problem in the first place.
To see any graphs, charts, graphics, images or studies mentioned here, please go to the Nutrition Facts podcast landing page. There, you’ll find all the detailed information you need – plus links to all the sources we cite for each of these topics.
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