By Alexander Angeloff, founder of TranscenDental. Educational content, not a substitute for advice from your dentist or doctor.
Sodium lauryl sulfate (SLS) is the detergent that makes most toothpaste foam. For most people it's harmless. For some, especially people who get frequent canker sores or have a dry, easily irritated mouth, going SLS-free can make a real difference.
This guide covers what SLS-free toothpaste is, who it actually helps, what the research shows, whether Sensodyne is SLS-free, and how to read a label so you know what you're getting instead.
In short: SLS-free toothpaste is any toothpaste made without sodium lauryl sulfate. The best evidence is for canker sores: a 2019 meta-analysis found fewer, shorter and less painful ulcers with SLS-free toothpaste. Many "SLS-free" pastes swap in a milder foaming detergent, so if your mouth is very sensitive, check what replaced it.
What I brush with every day
What is SLS-free toothpaste?
Sodium lauryl sulfate is a synthetic anionic surfactant, a detergent that lets water and oil mix. It's in shampoo, body wash and most conventional toothpastes, where it does two jobs: it makes the paste foam and it helps spread it around your mouth.
An SLS-free toothpaste simply leaves it out. What it uses instead varies a lot:
- A milder foaming detergent, such as cocamidopropyl betaine or sodium methyl cocoyl taurate. This is what most "SLS-free" toothpastes do.
- A sulfate under another name, such as sodium coco-sulfate, which is made from coconut oil and is largely SLS. Some "sulfate-free"-looking natural brands use it.
- No foaming detergent at all. These pastes foam very little and rely on brushing, gentle abrasives and emulsifiers to do the work.
Foam feels like cleaning, but brushing is what removes plaque. A randomized trial found an SLS-free toothpaste performed as well as an SLS toothpaste for plaque and gingivitis (Salzer et al., 2016).
Is SLS in toothpaste bad for you?
For most people, no. SLS is approved for use in toothpaste and the amounts are small. But it isn't completely inert in the mouth:
- It can irritate the lining of the mouth. A 2022 scoping review in the American Journal of Dentistry listed mucosal peeling, irritation, inflammation and ulcers as the side effects reported in studies (Kasi et al., 2022).
- It's harsher than its milder replacements. In a Norwegian experiment, brushing with an SLS toothpaste for four days caused 42 tissue-peeling reactions, compared with 3 for a cocamidopropyl betaine paste and none for a detergent-free paste (Herlofson & Barkvoll, 1996).
- It's behind the "orange juice effect". SLS is widely thought to explain why food and drinks taste bitter right after brushing, because it temporarily dulls sweet taste.
The people most likely to notice a difference are those with recurrent canker sores, dry mouth or a mouth that's already inflamed, for example from gingivitis or a cut on the gums.
SLS-free toothpaste for canker sores
This is where the evidence is strongest. Canker sores (recurrent aphthous stomatitis) are small, painful ulcers inside the lips, cheeks or under the tongue.
- A 2019 meta-analysis in the Journal of Oral Pathology & Medicine pooled four small crossover trials. With SLS-free toothpaste, people had fewer ulcers, fewer episodes, less pain, and ulcers that healed about two days faster. The authors said patients "may benefit" but called for better trials.
- Not every trial agrees. One 47-person trial found no significant difference (Healy et al., 1999), while a 90-person Korean trial found no change in how often ulcers appeared but shorter, less painful ulcers with SLS-free paste (Shim et al., 2012).
- The type of replacement may matter. In a three-way trial, an SLS paste caused the most ulcers, a cocamidopropyl betaine paste fewer, and a detergent-free paste significantly fewer than either (Herlofson & Barkvoll, 1996, as summarized by NutritionFacts).
What this means in practice: if you get canker sores often, switching to an SLS-free toothpaste for two or three months is a low-risk experiment. If a milder-detergent paste doesn't help, a detergent-free one is the next step. Canker sores also have other triggers, including stress, minor injuries and some nutrient deficiencies, so see your dentist or doctor if they're frequent, large or slow to heal.
SLS-free toothpaste for dry mouth
A dry mouth has less saliva to protect its lining, so detergents tend to sting more. Dry mouth guides commonly recommend an SLS-free toothpaste for this reason.
One ingredient with some trial evidence is betaine (trimethylglycine), a natural compound from sugar beets. In a small double-blind crossover trial from the University of Turku, a 4% betaine toothpaste relieved several dry mouth symptoms compared with the same paste without it (Söderling et al., 1998). Betaine is not the same thing as cocamidopropyl betaine, the foaming detergent; the names are confusingly similar.
Xylitol also helps some people with dry mouth because it stimulates saliva. A slow-dissolving xylitol mint after meals is an easy way to add it.
SLS-free toothpaste for sensitive teeth
Tooth sensitivity comes from exposed dentin, usually from enamel wear or receding gums. There isn't good evidence that SLS causes sensitivity, so going SLS-free on its own won't fix it.
What does help is a low-abrasion toothpaste with an ingredient that blocks the tiny tubules in exposed dentin. Hydroxyapatite has shown benefits for sensitivity in clinical studies (see our guide to nano-hydroxyapatite toothpaste). If your gums are also tender, an SLS-free formula is a sensible choice on top of that.
What I brush with every day
10% nano-hydroxyapatite, organic birch xylitol and 2% theobromine in a probiotic herbal ferment. No fluoride, SLS or glycerin.
Perioral dermatitis and SLS allergy
Perioral dermatitis is a rash around the mouth. Some people find it flares with certain toothpastes, and switching to an SLS-free, fluoride-free paste is commonly suggested. The evidence is mostly anecdotal, but it's an easy change to try alongside your dermatologist's advice.
A true SLS allergy is uncommon. More often SLS acts as an irritant rather than an allergen. If you suspect you react to an ingredient, a dermatologist can patch test you.
Is Sensodyne SLS-free?
Some Sensodyne toothpastes are and some aren't. Many Sensodyne and Pronamel products use cocamidopropyl betaine instead of SLS, while some lines, such as Repair & Protect in the US, have listed sodium lauryl sulfate (source). Formulas differ by country and change over time, so the inactive ingredients on the box are the only reliable answer.
Also worth knowing: SLS-free Sensodyne isn't detergent-free. If you've tried it and still get canker sores or irritation, the cocamidopropyl betaine may be worth avoiding too.
SLS-free toothpaste list: how to read the label
Brand lists go out of date quickly, so here's how to sort any toothpaste yourself. Look at the ingredients (or "inactive ingredients" in the US) for these:
| What the label says | What it is |
|---|---|
| Sodium lauryl sulfate, sodium laureth sulfate | Sulfate detergents. Not SLS-free. |
| Sodium coco-sulfate | Coconut-derived sulfate, mostly SLS. Technically "SLS-free" on some labels, but not in practice. |
| Cocamidopropyl betaine, sodium methyl cocoyl taurate, sodium cocoyl glutamate, sodium lauroyl sarcosinate, coco or decyl glucoside | Milder foaming detergents. SLS-free, but not detergent-free. |
| None of the above | Detergent-free. Expect little or no foam. |
Ingredients like sunflower lecithin or plant gums are emulsifiers and thickeners, not foaming detergents.
Fluoride-free and SLS-free toothpaste
Many people looking for SLS-free toothpaste also want to avoid fluoride. The key is making sure the paste still has something to protect enamel. Hydroxyapatite is the best-studied option: in clinical trials it performed about as well as fluoride for preventing new decay. We compare the research in hydroxyapatite vs fluoride and explain what to look for in the best fluoride-free toothpaste.
What we use instead of SLS
TranscenDental toothpaste contains no SLS and no synthetic foaming detergents: no SLES, sodium coco-sulfate, cocamidopropyl betaine or glucosides. Here's what does the work instead:
- Sunflower lecithin, a natural plant emulsifier that keeps the oils and minerals evenly mixed without making foam.
- Hyaluronic acid, which gives the paste body and is used in gum care for its hydrating properties. More in hyaluronic acid for gums.
- Betaine (trimethylglycine), the same ingredient studied for dry mouth above.
- Baking soda and bentonite clay as gentle cleaning agents.
- 10% dual-particle nano-hydroxyapatite for enamel, plus organic birch xylitol and 2% theobromine.
It's also free of fluoride, glycerin, silica and charcoal, and it comes in a glass jar instead of a plastic tube. For the bigger picture on choosing a clean formula, see what makes the best natural toothpaste.
What to expect when you switch
- Less foam. It feels different for a few days. It doesn't mean it's cleaning less.
- No bitter aftertaste with your morning coffee or juice.
- A calmer mouth for many people with sensitive tissue. If you get canker sores, give it two to three months to judge.
Build the full routine: brush with TranscenDental toothpaste, clean between your teeth with our plastic-free bamboo floss, and finish after meals with an Ora Flora xylitol mint (about 3 g of organic birch xylitol each, no gum base or artificial sweeteners). Or get all three together in the Oral Care Trio and save $12.
Frequently asked questions
What does SLS-free toothpaste mean?
It means the toothpaste doesn't contain sodium lauryl sulfate. It may still contain a different, usually milder, foaming detergent, so check the label if you want a detergent-free paste.
Does SLS-free toothpaste clean as well?
Yes. Foam isn't what removes plaque; brushing is. Trials have found SLS-free toothpaste works as well for plaque and gingivitis.
Does SLS-free toothpaste help canker sores?
For many people, yes. A 2019 meta-analysis found fewer, shorter and less painful ulcers with SLS-free toothpaste, though the trials were small and results varied.
Is Sensodyne SLS-free?
Many Sensodyne and Pronamel toothpastes are SLS-free and use cocamidopropyl betaine instead, but not all. Check the ingredients on the specific product you buy.
Is sodium coco-sulfate the same as SLS?
Not exactly, but it's made largely of the same compound. If you're avoiding SLS for irritation or canker sores, treat it the same way.
Is SLS-free toothpaste good for dry mouth?
It's commonly recommended because detergents tend to irritate a dry mouth more. Look for one that's also gentle in flavor and, ideally, contains betaine or xylitol.
Can you be allergic to SLS?
True allergy is uncommon; irritation is much more common. If you suspect a reaction, a dermatologist can patch test you.
Is SLS-free toothpaste better for kids?
Children who get canker sores may benefit the same way adults do. Use the amount your dentist recommends for their age, and choose a flavor they'll actually brush with.
What I brush with every day
10% nano-hydroxyapatite, organic birch xylitol and 2% theobromine in a probiotic herbal ferment. No fluoride, SLS or glycerin.
