Squeeze some toothpaste onto your brush and you’ll probably notice the foam before you notice anything else. That foam is often produced largely by surfactants such as sodium lauryl sulfate, or SLS, though the exact ingredients vary by formulation. SLS is used in many conventional toothpastes, and it’s also one of the most-searched “should I avoid this” ingredients in oral care, mainly because of its link to canker sores.
So what is SLS actually doing in your toothpaste, and is the concern warranted? Here’s what the research says.
MEDICAL DISCLAIMER: This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before taking supplements or making dental health changes. If you experience unusually severe, persistent, or frequently recurring mouth ulcers, see a dentist or physician.
AFFILIATE DISCLOSURE: This article contains affiliate links. If you purchase through these links, we may earn a commission at no extra cost to you.
Quick Answer: What Does SLS Do in Toothpaste?
SLS (sodium lauryl sulfate) is a detergent-like surfactant used in many toothpastes to create foam and help the toothpaste spread during brushing. SLS is not inherently harmful to everyone, but some evidence suggests people with recurrent aphthous ulcers may benefit from using SLS-free toothpaste. Research is mixed, so SLS should not be described as universally harmful or as a cause of mouth ulcers in everyone.
What Is SLS in Toothpaste?
SLS stands for sodium lauryl sulfate. In toothpaste, it’s primarily used as a surfactant and foaming agent that helps the toothpaste spread during brushing and creates the familiar foam.
It’s commonly listed on ingredient labels as “sodium lauryl sulfate.” “Sodium dodecyl sulfate” is a chemical synonym you may encounter in research literature, though product labels typically stick with the more common name. A surfactant is an ingredient that reduces surface tension between substances, letting the toothpaste mix more easily with saliva and water so it spreads across your teeth and gums instead of staying in one thick mass on your brush. Manufacturers use SLS because it’s inexpensive, effective at producing foam, and gives toothpaste the texture and rinsing experience most people expect.
SLS in toothpaste = a surfactant/foaming ingredient used primarily for formulation and brushing experience.
What Does SLS Actually Do in Toothpaste?
SLS Creates Foam
The foam you see when you brush often comes largely from SLS when the toothpaste contains it. Toothpaste foams because SLS lowers the surface tension of the paste-saliva mixture, trapping air as you brush. More foam doesn’t necessarily mean better cleaning, though; foam volume is a cosmetic and sensory effect, not a direct measure of how well plaque is being removed. Foam itself isn’t what removes plaque: mechanical brushing, together with the toothpaste’s abrasives and other formulation components, does the cleaning, while fluoride or another active ingredient handles cavity prevention separately.
SLS Helps Toothpaste Spread
As a surfactant, SLS helps the toothpaste spread and interact with water during brushing, distributing it across your teeth, gums, and tongue. The clinical significance of this distribution depends on the complete formulation and your brushing technique, not on SLS alone.
SLS Is Not the Main Cavity-Fighting Ingredient
This distinction matters: SLS performs a formulation role, while anticaries active ingredients such as fluoride provide the main cavity-prevention benefit. Other ingredients, including hydroxyapatite, may also be used for tooth remineralization or caries prevention, depending on the formulation and the evidence supporting that specific product. SLS itself does not provide the main anticaries benefit; that job belongs to the toothpaste’s active ingredient, not its surfactant.
What SLS Does and Doesn’t Do
| SLS Does | SLS Does Not |
| Creates foam | Provide the main cavity-prevention benefit |
| Acts as a surfactant | Automatically make toothpaste more effective |
| Helps toothpaste spread | Mean that a toothpaste is inherently harmful |
| Contributes to the brushing experience | Mean that everyone needs to avoid SLS |
Why Is SLS Used in Toothpaste?
| Function | What It Means |
| Surfactant | Helps the toothpaste interact with water and spread |
| Foaming agent | Produces foam during brushing |
| Formulation ingredient | Helps create the desired toothpaste texture and consistency |
| User experience | Provides the familiar foaming sensation people expect |
Is SLS Bad for Your Teeth?
Current evidence does not support describing SLS as universally harmful to teeth, but some people may experience oral irritation or may prefer SLS-free toothpaste because of recurrent mouth-ulcer symptoms.
What’s established:
- SLS is commonly used as a toothpaste surfactant
- It contributes to foaming
- Individual tolerance varies
What’s less certain:
- Whether SLS directly causes recurrent aphthous ulcers
- Whether everyone with mouth ulcers benefits from removing SLS
- Whether SLS-free toothpaste is universally preferable
Does SLS Cause Canker Sores?
SLS shouldn’t be described as a universal cause of canker sores. However, several clinical studies and a systematic review suggest that people with recurrent aphthous stomatitis may experience fewer or less painful ulcers when using SLS-free toothpaste.
A small preliminary 1994 study following 10 patients with recurrent aphthous ulcers found a statistically significant drop in ulcer frequency after switching from an SLS-containing to an SLS-free dentifrice. A 1996 double-blind crossover study of 30 patients found a significantly higher frequency of aphthous ulcers during the SLS phase than during the CAPB-containing or detergent-free phases. A later 2012 randomized controlled crossover trial of 90 subjects produced more mixed results: it found no significant difference in the total number of ulcers or episodes between SLS and SLS-free phases, though ulcer duration and pain were lower during the SLS-free phase. A 2019 systematic review of four crossover randomized controlled trials involving 124 participants found that SLS-free toothpaste was associated with reductions in ulcer number, duration, episodes, and pain. However, the authors noted that the evidence base was limited and that better-designed trials were needed.
The evidence-based takeaway: SLS-free toothpaste may benefit some people with recurrent aphthous ulcers, but SLS is not established as a universal cause of canker sores.
Evidence at a Glance
| Question | What the Evidence Suggests | Confidence / Limitation |
| Does SLS create foam? | Yes; this is a primary formulation function | Well established |
| Does SLS prevent cavities? | No; it is not the primary anticaries active ingredient | Clear distinction |
| Does SLS cause canker sores in everyone? | No evidence supports this broad claim | Avoid overstatement |
| Can SLS-free toothpaste help people with recurrent ulcers? | Some evidence suggests potential benefit | Evidence is limited/mixed |
| Should everyone avoid SLS? | Not necessarily | Individual tolerance matters |
What Does Research Say About SLS and Oral Ulcers?
1994: Preliminary clinical study. A small study of 10 patients with recurrent aphthous ulcers found ulcer frequency dropped significantly after switching from an SLS-containing to an SLS-free dentifrice.
1996: Double-blind crossover study. A 30-patient trial comparing SLS-containing, CAPB-containing (cocamidopropyl betaine, another surfactant), and detergent-free toothpaste found a significantly higher frequency of aphthous ulcers during the SLS phase.
2012: Randomized controlled crossover trial. A 90-subject double-blind trial, using 8-week treatment periods with a 2-week washout, found no significant difference in the number of ulcers or episodes between SLS and SLS-free phases, though ulcer duration and pain were both reduced during the SLS-free phase.
2019: Systematic review. A review of four crossover randomized controlled trials (n=124) found statistically significant reductions in ulcer number, duration, episodes, and pain with SLS-free dentifrice, while noting that only four trials were available and calling for better-designed research.
Overall conclusion: The evidence leans toward a potential benefit from SLS-free toothpaste for people with recurrent aphthous ulcers, but it doesn’t establish that SLS causes ulcers in everyone.
Who Might Benefit From SLS-Free Toothpaste?
People who frequently experience recurrent mouth ulcers or notice irritation when brushing may consider trying an SLS-free toothpaste.
This can include people with:
- Recurrent aphthous ulcers (canker sores)
- General oral sensitivity or a burning sensation after brushing
- Irritation they’ve traced to a particular toothpaste formulation
- A personal preference for milder-foaming formulas
To be clear: this isn’t the same as saying everyone with sensitive teeth should avoid SLS; that’s a broader claim the current evidence doesn’t support.
Is SLS-Free Toothpaste Better?
SLS-free toothpaste isn’t automatically better for everyone. Its main potential advantage is that it may be more comfortable for some people who experience oral irritation or recurrent aphthous ulcers.
| Toothpaste With SLS | SLS-Free Toothpaste | |
| Foam | Usually more | Usually less |
| Contains SLS | Yes | No |
| Cavity protection | Depends on active ingredients | Depends on active ingredients |
| Oral comfort | Well tolerated by many | May suit some people with irritation |
| Best for | Personal tolerance | People with ulcer sensitivity |
How to Check If Your Toothpaste Contains SLS
Look at the ingredient list on your current tube for “sodium lauryl sulfate.” A few practical notes:
- Formulas change, sometimes without much fanfare; a brand you remember as SLS-containing may have reformulated, and vice versa
- Always check the package you actually have, not an old memory of the ingredient list
- Don’t assume every product line from a brand shares the same formula; a brand can sell both SLS-containing and SLS-free versions side by side
Amazon Affiliate Product: Boka Ela Mint Nano-Hydroxyapatite Toothpaste
Why it fits: Boka Ela Mint is a relevant example for readers looking for an SLS-free toothpaste. It also uses nano-hydroxyapatite, giving readers an alternative active-ingredient approach to conventional fluoride toothpaste.
Type: Fluoride-free nano-hydroxyapatite toothpaste
Key ingredient: Nano-hydroxyapatite
Why consider it: SLS-free formulation with nano-hydroxyapatite as the featured active ingredient.
Best for: Readers looking for an SLS-free, fluoride-free toothpaste and interested in hydroxyapatite-based formulations.
SLS Alternatives in Toothpaste
Some toothpastes use other surfactants instead of SLS, including cocamidopropyl betaine or sodium cocoyl glutamate, while others use little or no foaming agent at all.
These ingredients can have different tolerability profiles, but no alternative is automatically suitable for everyone. Different surfactants can provide similar formulation functions, but the suitability of an ingredient depends on the complete formulation and individual tolerance; swapping in an alternative surfactant isn’t automatically “safer” on its own.
Amazon Affiliate Product: Sensodyne Fresh Mint
Why it fits: Sensodyne Fresh Mint provides an example of an SLS-free toothpaste for readers who want to avoid SLS while still using a conventional fluoride-based toothpaste.
Type: SLS-free fluoride toothpaste
Key active ingredient: Fluoride
Why consider it: Provides a different approach from fluoride-free hydroxyapatite toothpaste.
Best for: Readers looking for an SLS-free toothpaste that retains fluoride-based cavity protection.
Should You Avoid SLS in Toothpaste?
You don’t necessarily need to avoid SLS if you tolerate it well. However, if you experience recurrent mouth ulcers or oral irritation, you could ask your dentist whether trying an SLS-free toothpaste for several weeks is appropriate, while continuing to use a product with an effective anticaries active ingredient, such as fluoride. For a broader review of toothpaste ingredients and the evidence behind potential concerns, see VitaDent Labs’ guide to toothpaste ingredients to avoid.
SLS-Free Toothpaste Options to Consider
Now that you understand why someone might choose an SLS-free toothpaste, the following products provide examples of different formulations. They are not ranked; the right choice depends on factors such as your oral-health needs, active ingredients and individual tolerance.
| Product | Type | Key Ingredient | CTA |
|---|---|---|---|
| Boka Ela Mint | SLS-free, fluoride-free toothpaste | Nano-hydroxyapatite | Check Price on Amazon |
| Sensodyne Fresh Mint | SLS-free fluoride toothpaste | Fluoride | Check Price on Amazon |
Frequently Asked Questions
What does SLS do in toothpaste?
Is SLS bad for your teeth?
Does SLS cause canker sores?
Is SLS-free toothpaste better?
What is SLS-free toothpaste?
Why does SLS make toothpaste foam?
Should I avoid SLS in toothpaste?
Does SLS clean your teeth?
Final Thoughts
SLS isn’t the villain some ingredient lists make it out to be, and it isn’t essential to a toothpaste’s effectiveness either. It’s primarily a formulation ingredient rather than a therapeutic one: it helps toothpaste foam and spread, and that’s the extent of its role. If you tolerate your current toothpaste well, there’s no research-backed reason to switch. If you deal with recurrent canker sores, asking your dentist about trying an SLS-free formula for a few weeks may be a reasonable way to see whether your symptoms improve, as long as your replacement toothpaste still contains an effective active ingredient like fluoride. For a wider look at other ingredients worth understanding, see our guide to toothpaste ingredients to avoid.
Looking for an SLS-free option? If you’re considering switching toothpaste because of oral irritation or recurrent canker sores, you can compare the current Boka Ela Mint and Sensodyne Fresh Mint options above and check their latest formulations and availability on Amazon.
Evidence Reviewed
This article is based on clinical research and systematic-review evidence examining SLS-containing and SLS-free toothpastes, particularly studies involving recurrent aphthous ulcers.
References
Herlofson BB, Barkvoll P. Sodium lauryl sulfate and recurrent aphthous ulcers. A preliminary study. Acta Odontologica Scandinavica. 1994 Oct;52(5):257-9. https://doi.org/10.3109/00016359409029036
Herlofson BB, Barkvoll P. The effect of two toothpaste detergents on the frequency of recurrent aphthous ulcers. Acta Odontologica Scandinavica. 1996;54(3):150-153.
https://doi.org/10.3109/00016359609003515
Shim YJ, Choi JH, Ahn HJ, Kwon JS. Effect of sodium lauryl sulfate on recurrent aphthous stomatitis: a randomized controlled clinical trial. Oral Diseases. 2012 Oct;18(7):655-60.
https://doi.org/10.1111/j.1601-0825.2012.01920.x
Alli BY, Erinoso OA, Olawuyi AB. Effect of sodium lauryl sulfate on recurrent aphthous stomatitis: A systematic review. Journal of Oral Pathology & Medicine. 2019 May;48(5):358-364.
https://doi.org/10.1111/jop.12845
