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Gentian Violet: Deep Purple Dye Kills Some Cancer Cells, Early Research Finds

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It was like "Harold's Purple Crayon" run amok. The purple went everywhere — skin, diapers, clothes and, most of all, my baby's toothless mouth, suddenly stained deep purple as if she were wearing Goth lipstick.

We'd been fighting thrush — a stubborn yeast infection that often affects breastfeeding mothers and their babies' mouths — and the anti-fungal ointment prescribed by the pediatrician had made no dent.

In desperation, and despite my usual insistence on medical evidence from 21st-century clinical trials rather than 19th-century lore, I'd turned to gentian violet, an over-the-counter dye traditionally used for its anti-fungal and antibacterial effects.

Baby Ashley, whose parents are fighting thrush with gentian violet (Courtesy Edwin and Kelly Tofslie/Flickr)
Baby Ashley, whose parents are fighting thrush with gentian violet (Courtesy Edwin and Kelly Tofslie/Flickr)

An eyedropper pulled the purplest of purples — surely the oddest potion I've ever employed for health purposes — up from the little vial it came in.

And it worked. End of thrush. Worth every purple splotch.

That old memory flooded back at the sight of a new journal article suggesting that the deep purple remedy may turn out to have some power against a rare form of cancer as well. The paper analyzed gentian violet's ability to kill tumor cells in a rare, slow-growing type of skin cancer called cutaneous T-cell lymphoma.

The early study — only in test tubes, not even in rodents yet — concludes that the dye "attacked tumor viability and growth" and is worth studying as a potential "novel, inexpensive, topical therapy" that could be used worldwide.

It adds to a growing body of evidence -- headlined "A 19th-Century Drug Re-Emerges In The 21st Century" — that gentian violet has multiple useful qualities, including anti-cancer potential.

The researchers did not set out to study gentian violet specifically. They ran more than 1,700 compounds through testing to detect effects on the lymphoma, and found that the violet looked like a potent killer of cancer cells. (And, they note, it doesn't have to stain everything deep purple; changing its pH can make it colorless but still effective.)

If gentian violet does emerge after further study as a useful weapon against cancer, it would not be the first discovery of anti-cancer properties in unexpected places. The chemotherapy drug Taxol is famously derived from the bark of the Pacific yew tree. Another class of chemotherapy is derived from the periwinkle plant.

But let's not get ahead of ourselves. First, the inevitable caveats.

"I certainly wouldn't encourage folks with cutaneous T-cell lymphoma to forego more established treatments and run out and get gentian violet," said Dr. Eric Jacobsen, clinical director of the Lymphoma Program at the Dana-Farber Cancer Institute.

Just to reinforce that message: A study this summer found that cancer patients who chose alternative medicine over conventional treatment were twice as likely to die over a decade.

"But [gentian violent] certainly warrants further study," Jacobsen said.

Studies like the new research on gentian violet serve to generate a hypothesis worth exploring, he said. "The downside is, sometimes you find a lot of noise, so to speak — things that look good in the lab that don't translate into patients."

The next step would generally be to test in animals, Jacobsen said. Though, given that the lymphoma tends to be chronic and the violet is generally safe, he added, "I think it also wouldn't be unreasonable to make the leap from this study to a small human trial, to see if you can demonstrate some actual efficacy in patients."

To test the violet in humans, researchers would also need to determine the proper formulation and dosing.

There are plenty of existing treatments for cutaneous T-cell lymphoma, Jacobsen said; most treatments can be topical — applied to the skin; few patients progress to needing chemotherapy and radiation; and patients rarely die of it.

But the existing treatments often stop working or don't work at all. And some patients suffer from terrible itching.

Also, "there is a need for less expensive therapies," Jacobsen said. "Some of the topical therapies that we use are surprisingly expensive" — thousands of dollars — "and often the co-payment can be prohibitive for patients."

If current prices are any indication — vials of gentian violet antiseptic sell for a few dollars online — gentian violet treatments for cancer would be a far cheaper option. That would be good for patients paying out of pocket — but on the other hand, if there's little prospect of commercial gain, that could limit gentian violet's chances of being developed into a proven treatment.

Jacobsen has seen other compounds that appeared to show promise in the lab — like a component of green tea, and the spice curcumin — fail to gain traction.

If a patient of his were to express interest in trying gentian violet now, he said, he would respond that ideally it should be studied first in a clinical trial. If the patient wanted to try it anyway, it is non-toxic enough that he would not be worried, he said, but he would just want to know that they were using it.

"People are free to respect their physician's opinion or not on the utility of these things," he said, "but if they choose to use them, I think it's important they let their physician know about it."

Stacy Kennedy, a senior clinical nutritionist at Dana-Farber, reinforced that "tell your medical team" message:

"The research is still showing that while up to 90 percent of [cancer] patients in any given year might be taking a complementary or alternative medicine approach, there's still a very low number who are actually discussing this with their oncologist" — less than half, she said.

Any time a patient reads a study like the paper on gentian violet, she said, "I want them to come talk to me about it."

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Carey Goldberg Twitter Editor, CommonHealth
Carey Goldberg is the editor of WBUR's CommonHealth blog.

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