Friday Favorites: Does Tea Tree Oil Work for Dandruff, Athlete’s Foot, and Nail Fungus?

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Tea tree oil is touted as having antifungal properties. So what happens when it’s put to the test for a variety of fungal infections? Watch the video to find out.

Our entire understanding of the cause of dandruff shifted with this 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 a 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. Looks like more than 40% from the graph, but that’s because they misleadingly started the Y-axis at -60. This is a classic deception featured in chapter 5 of the 1954 classic How to Lie with Statistics. The graph should really look like this, which makes the effect less impressive, but it was still statistically significant.

“[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 appears 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 the 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, and here’s the dental plaque buildup after 4 days of no brushing swishing with a placebo. Here’s swishing with a medicated chlorhexidine mouthwash, which keeps the plaque a bit at bay, but the tea tree oil mouth rinse? No effect.

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.

Might the same thing be happening here? Yeah, from a mycological cure standpoint—a fungus cure standpoint—tea tree oil didn’t really do any better than placebo. But, though the drug wiped out the fungus in 85% of cases, in some of those cases, the patients actually didn’t notice an improvement in symptoms, or they actually felt worse after the drug—probably a reflection of tinactin’s “irritant side effect[s].” If instead of mycological cure, you looked at symptom improvement, tea tree oil works as well as the drug. 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 that 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.

“Onychomycosis is a fungal infection” of our nails—usually toenails, but sometimes fingernails—characterized by nail discoloration, deformity, detachment, “thickening, crumbling, ridging.” Here’s an example of what it can look like.

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.

Tea Tree Oil vs. Common Drugs

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 this study of a combination of the antifungal drug in Lotrimin cream with tea tree oil that seemed pretty effective—compared to nothing. But, what about compared to each other? 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, or 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.”

Treating the Underlying Cause

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 try to instead improve the circulation?

We’ve known since the 1950s 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.

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• Thosar N, Basak S, Bahadure RN, Rajurkar M. Antimicrobial efficacy of five essential oils against oral pathogens: An in vitro study. Eur J Dent. 2013;7(Suppl 1):S71-7.
• Arweiler NB, Donos N, Netuschil L, Reich E, Sculean A. Clinical and antibacterial effect of tea tree oil--a pilot study. Clin Oral Investig. 2000;4(2):70-3.
• Soukoulis S, Hirsch R. The effects of a tea tree oil-containing gel on plaque and chronic gingivitis. Aust Dent J. 2004;49(2):78-83.
• Satchell AC, Saurajen A, Bell C, Barnetson RS. Treatment of dandruff with 5% tea tree oil shampoo. J Am Acad Dermatol. 2002;47(6):852-5.
• Shuster S. The aetiology of dandruff and the mode of action of therapeutic agents. Br J Dermatol. 1984;111(2):235-42.
• Hammer KA, Carson CF, Riley TV. Antifungal activity of the components of Melaleuca alternifolia (tea tree) oil. J Appl Microbiol. 2003;95(4):853-60.
• Benger S, Townsend P, Ashford RL, Lambert P. An in vitro study to determine the minimum inhibitory concentration of Melaleuca alternifolia against the dermatophyte Trichophyton rubrum. The Foot. 2004;14(2):86-91.
• Tong MM, Altman PM, Barnetson RS. Tea tree oil in the treatment of tinea pedis. Australas J Dermatol. 1992;33(3):145-9.
• Satchell AC, Saurajen A, Bell C, Barnetson RS. Treatment of interdigital tinea pedis with 25% and 50% tea tree oil solution: a randomized, placebo-controlled, blinded study. Australas J Dermatol. 2002;43(3):175-8.
• Bergstrom KG. Tea tree oil: panacea or placebo?. J Drugs Dermatol. 2009;8(5):494-6.
• Buck DS, Nidorf DM, Addino JG. Comparison of two topical preparations for the treatment of onychomycosis: Melaleuca alternifolia (tea tree) oil and clotrimazole. J Fam Pract. 1994;38(6):601-5.
• Halteh P, Scher RK, Lipner SR. Over-the-counter and natural remedies for onychomycosis: do they really work?. Cutis. 2016;98(5):E16-E25.
• Syed TA, Qureshi ZA, Ali SM, Ahmad S, Ahmad SA. Treatment of toenail onychomycosis with 2% butenafine and 5% Melaleuca alternifolia (tea tree) oil in cream. Trop Med Int Health. 1999;4(4):284-7.
• Kuo PT, Whereat AF, Horwitz O. The effect of lipemia upon coronary and peripheral arterial circulation in patients with essential hyperlipemia. Am J Med. 1959;26(1):68-75.

Image credit: Benjamin Zanatta via Unsplash. Image has been modified.

Motion graphics by Avocado Video.