Is Cocamidopropyl Betaine in Toothpaste Better Than Sodium Lauryl Sulfate?

For those with recurrent canker sores, is it better to use a toothpaste with SLS, CAPB, or no foaming agents at all?

Sodium lauryl sulfate (SLS) had already been used as a foaming agent in toothpastes for more than a half-century by the time a study was published showing tissue damage in most of those who had it smeared on their gums—but that was “most” of only ten study subjects. Same with a study finding a dramatic decrease in the number of canker sores when people switched to an SLS-free toothpaste. (Again, just ten people.)

But, that’s all we had until 1999, when a randomized, double-blind, crossover trial was published, testing SLS against non-SLS toothpaste in not just 10 people, but 47 people, with recurrent canker sores. The study looked at the number of days of suffering, total pain, number of ulcers, how long they lasted, and how big they were, and no significant differences were noted. It didn’t seem to matter whether the toothpaste had sodium lauryl sulfate or not. But what about that study showing the 70 percent decrease in canker sores after switching to an SLS-free toothpaste? Well, maybe those cases were worse and the type of toothpaste used only matters if you have really bad canker sores?

That’s where the science ended until 13 years later when Korean researchers picked up the torch. We had studies showing SLS-free toothpaste helps and other studies finding no benefit, leading to “considerable controversy,” so they launched the biggest study to date with 90 subjects. What did they find? The same number of ulcers and ulcer episodes among the groups, but the duration the ulcers lasted and average pain score were significantly decreased when subjects were using the SLS-free toothpaste. So, the researchers concluded that switching to an SLS-free toothpaste may not reduce the number of canker sores you get, but it may allow them to heal faster and make them less painful. 

So, yes, sodium lauryl sulfate “creates an impression of cleanliness, and a mouthful of foam ‘just feels cleaner,’” but the potential downside may be that “SLS reduces the protective barrier of the oral epithelium,” our mouth lining, probably due to the rupture of the bonds that hold our cells together. This can sometimes cause sloughing, ulcerations, and inflammation that dry out the protective mucous layer lining our mouth, making us more vulnerable to irritants. 

Hold on. How did the Korean researchers explain that their study found a problem, but the previous study didn’t? They suggested it could be a race issue. Really? Well, they explained that “Koreans eat more hot and spicy food,” so maybe that makes a difference?

Regardless of how spicy you like your food, if you get canker sores, you may want to give an SLS-free toothpaste a try to see if it makes any difference for you—but non-SLS toothpaste may just have other detergents, most commonly cocamidopropyl betaine (CAPB). As I discuss in my video, Is CAPD in SLS-Free Toothpaste Any Better? Swiss researchers took nine toothpastes, including Colgate, Crest, Oral-B, and Sensodyne, and dripped them on some human gum cells taken fresh from people who had their wisdom teeth extracted. They then used live-dead cell staining: All the cells were dyed green, and then a red dye was added that covers up the green dye, but only in dead cells, because the live cells actively pump out the red dye. So, the live cells stay green, but the dead cells turn red. As you can see at 3:25 in my video, Colgate contains SLS because the cells are all red and all dead. And Crest? The cells are mostly red and mostly dead. But with SLS-free Sensodyne, the cells are all green and all alive because it contains the SLS-free detergent CAPB instead.

But that was in a petri dish. Does that translate out into actual tissue damage in people? A double-blind crossover study of SLS-containing toothpastes versus CAPB-containing toothpastes found 42 desquamative reactions, meaning tissue peeling reactions, after four days of four minutes a day of the SLS toothpaste on subjects’ gums, compared to just three reactions with the alternate detergent, CAPB. And there were no such reactions at all using the exact same toothpaste with no SLS or CAPB at all—detergent-free toothpaste.  

How does this translate out into canker sore frequency? A randomized, double-blind, crossover study investigated the effect of toothpastes containing SLS, CAPB, or no detergent at all. The researchers found “significantly higher frequency” of canker sores when patients brushed with SLS-containing toothpastes rather than with non-SLS toothpastes, whether CAPB-containing or detergent-free, so they suggest that an “SLS-free toothpaste may thus be recommended for patients with recurrent aphthous ulcers,” canker sores. But, as you can see at 5:00 in my video, they found more than just that.

Yes, SLS was the worst, but the detergent-free, non-foaming toothpaste beat out both SLS and CAPB. Indeed, the non-foaming toothpaste caused significantly fewer ulcers than the non-SLS alternative detergent, CAPB, which in turn caused significantly fewer ulcers than the SLS toothpaste. So, the vast majority of recurrent canker sore patients would benefit by switching from a regular toothpaste to a non-foaming toothpaste, but most would benefit by staying away from SLS regardless. 

But if your toothpaste doesn’t have sodium lauryl sulfate, will it work as well? I’m not just talking about “the impression of cleanliness,” but actual effect on plaque and gingivitis? SLS may kill our cells, but it also kills bacteria, so is it possible an SLS-free toothpaste won’t work as well? It turns out that SLS-free toothpaste works just as well “with regard to reducing gingivitis and plaque,” so we can recommend it for those with recurrent canker sores. Sodium lauryl sulfate may make things worse by disintegrating the protective mucus layer and eventually penetrating into the deeper layers of the lining of our mouths, where “living tissue function may be compromised.”

Folks did miss the foaminess, though, of a toothpaste with SLS. There is one additional benefit to choosing SLS-free toothpaste: SLS also penetrates into our tongue and “interferes with the inner mechanisms of our taste cells.” It’s actually responsible for the “orange juice effect.” You know that weird taste you get from citrus right after you brush your teeth? SLS is evidently what’s mucking with your taste cells.

Sodium lauryl sulfate? Wasn’t that part of some internet hoax? I cover the background of that in my video Is Sodium Lauryl Sulfate Safe?.


For more tips on oral health, see:

You may also be interested in checking out my series on the pros and cons of oil pulling:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Is Sodium Lauryl Sulfate (SLS) in Toothpaste Safe?

Just because the sodium lauryl sulfate in toothpaste doesn’t cause cancer doesn’t mean it can’t cause problems.

Sodium lauryl sulfate (SLS) is a common detergent used in toothpaste. It was featured in a famous Internet hoax nearly 20 years ago. Colgate toothpaste contains SLS, which was supposedly proven to cause cancer, but at least buying Colgate rather than Crest, manufactured by Procter & Gamble, didn’t support Satan—or so claimed another famous hoax that alleged that “a large portion of the profits of Procter and Gamble products goes to support the Satanic Church.”

The hoax that SLS in toothpaste and hair care products was linked to cancer became so widespread the American Cancer Society was forced to publish a response to shampoo-poo the link. Read the organization’s “Debunking the Myth” article, “Radical chain e-mails have been flying through cyberspace stating Sodium Lauryl Sulfate or SLS, a common ingredient in many health and beauty aids, is known to cause cancer. This is not true, according to researchers.” So, I just ignored it all these years, until I was doing research on canker sores, those painful, shallow, gray ulcerations you can get inside your lip or cheek, also known as aphthous ulcers. They can often be set off by trauma, like when you accidentally stab yourself with a toothbrush, so it’s recommended to try not to bite your lip and to avoid SLS-containing toothpaste—not because of cancer, but because of irritation. That at least makes a little more sense. Why would a detergent, a soap chemical, be carcinogenic? Though, you could imagine how SLS, theoretically, could at least dissolve some of the protective layer from the inside of your mouth. So, I decided to look into it, as I discuss in my video Is Sodium Lauryl Sulfate Safe?.

Although SLS has been used as a foaming agent in toothpastes since the 1930s, our story begins 25 years ago with an abstract presented at a conference on the possible effects of SLS on recurrent canker sores. Researchers took ten men and women getting more than one sore a week, nearly 18 on average over a three-month period, who had been using a regular SLS-containing toothpaste, and switched them to an SLS-free toothpaste for another three months. The subjects went from 18 canker sores down to around 5—about a 70 percent decrease. The researchers thought the SLS was adversely affecting the protective mucus layer that lines the mouth.

You always have to be cautious about published abstracts, though. You should always make sure that researchers actually go on to publish their findings in a peer-reviewed medical journal. And, indeed, in this case, they did. So we can confirm they conducted a double-blind study and used the same toothpaste, one with the regular concentration of SLS and the other SLS-free, but still with just ten patients. Though it was considered a preliminary study, it apparently had such a dramatic effect that a series of experiments were performed to see what might be going on. Researchers simply applied some SLS at the concentration found in toothpaste onto someone’s gums with a Q-tip for 90 seconds and measured the spike in blood flow to the area, a sign of inflammation, presumably because the detergent was penetrating and irritating the gums, as you can see at 3:06 in my video. But does it actually damage the tissue?

Researchers smeared some toothpastes on the gums of some dental hygienists for two minutes twice a day for four days, and although the SLS-free toothpaste didn’t cause any problems, the ones with the typical amount of SLS caused “desquamation” among most of the participants—in other words, a sloughing off or peeling of the topmost layers of the inside lining of their mouths. No wonder SLS might make canker sores worse.

If you go back to the original American Cancer Society source debunking SLS as being cancer-causing, the response was that SLS is not a known carcinogen—it’s just a known irritant.

What about the non-SLS foaming agents? I discuss them in my video Is CABP in SLS-Free Toothpaste Any Better?.


I’ve taken a deep dive into canker sores. See, for example:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Topical Green Tea for Acne and Fungal Infections

Which plant should we use for which skin disease? That’s the topic of my video Natural Treatment for Acne and Fungal Infections. Thousands of studies have been published to date about the health effects of green tea, but it wasn’t until fairly recently that researchers began to look at the possibility of using green tea for the prevention and treatment of infections. Patents have been taken out on the antibacterial, antifungal, and antiviral properties of tea. Let’s review some of the evidence.

In terms of fungal infections, green tea compounds have demonstrated “potent antifungal activity” against the primary cause of athlete’s foot, fungal nail infections, jock itch, and ringworm—comparable, in some cases, to powerful antifungal drugs like fluconazole. This was shown in a petri dish, though. How about a green tea footbath for athlete’s foot fungus between the toes? Evidently, tea leaves were once used as a folk remedy for the fungus, so why not put it to the test? Indeed, a once-a-day, 15-minute dilute green tea footbath led to a significant improvement in symptoms compared to controls.

Green tea baths also appeared to help with fungus-associated atopic dermatitis, though there was no control group in that study, and a full-strength green tea may help clear candida yeast from poorly cleaned dentures. What about the bacteria that cause plaque and gingivitis? Even a 2% green tea mouthwash was found to be effective. Yes, you should be able to control plaque just with proper brushing and flossing—with an emphasis on “proper.” Most people don’t brush for the recommended four minutes a day, so a dilute green tea mouthwash may help.

In terms of plaque bacteria-killing ability, green tea was beaten out by a “garlic with lime mouth rinse,” but I think I’ll just stick to green tea, especially when green tea appears to not only kill plaque bugs directly but also boost the antibacterial capacity of saliva after you drink it.

What about green tea for acne? Six weeks of a 2% green tea lotion cut the number of pimples by more than half and significantly reduced the severity, as you can see at 2:48 in my video, making it a cheap, effective treatment for acne.

Impetigo is another bacterial skin infection that can affect the face, but a tea ointment can affect an 80 percent cure rate, on par with antibiotics given topically or orally.

What about bladder infections? We know a certain concentration of green tea compounds can kill the type of E. coli that causes urinary tract infections. The question then becomes how much tea do you have to drink to achieve those concentrations in your bladder? Not much, it turns out. Just one cup of tea might have an effect, but you may need to space out multiple cups over the day because it gets cleared out of your system within about eight hours, as you can see at 3:45 in my video.

So, where do we stand now? The test tube data look promising, but there has yet to be a single study to put it to the test. At this point, green tea should just be used as an adjunct therapy for bladder infections. But, with emerging multidrug-resistant organisms, green tea certainly holds potential.

Wait a moment. If green tea is so good at killing bacteria, might we be killing the good bacteria in our gut when we drink it? No. That’s what’s so amazing. “It has also been shown that green tea has no effect over intestinal flora, which is a great advantage against other bactericidal [bacteria-killing] agents.” But that may not actually be true. Drinking green tea may actually boost the levels of our good bacteria by acting as a prebiotic, thereby improving the colon environment, so it may actually have some effect on our gut flora after all, but it appears to be all good.


Drinking tea with meals may impair iron absorption, so it’s better to drink it between meals. For more on green tea, one of my favorite beverages, along with water and hibiscus tea, see:

For more on acne, check out:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: