Marketing claims
"SLS-free" is not the same as gentle
If a toothpaste foams and has no SLS in it, it contains a different foaming agent instead. "SLS-free" tells you one molecule is missing. It does not tell you what replaced it is any gentler.
What actually replaces it
Foam needs a surfactant. The usual stand-ins are cocamidopropyl betaine, sodium cocoyl isethionate, sodium lauroyl sarcosinate, sodium cocoyl glutamate and decyl glucoside.
Three of those five carry the same negative electrical charge as sodium lauryl sulfate. Charge matters, because it drives how strongly a surfactant pulls at the proteins in your tissue. None of this makes the replacements bad. It makes "SLS-free" a much weaker claim than it sounds.
Milder does not mean inert
Every replacement on that list is still built for the same basic job. Its oil-seeking tail can enter a fatty cell membrane while its water-seeking head remains in saliva. Given enough free surfactant and enough contact time, that interaction can loosen the membrane, make it leak and pull out lipids or proteins. At stronger laboratory exposures it can reduce cell survival or break the membrane apart.
That does not mean every substitute is as irritating as SLS, or that ordinary brushing kills oral tissue. Cocamidopropyl betaine has directly irritated human oral mucosa and reduced the survival of cultured gingival cells, although it is usually less irritating than SLS. For the other replacements, evidence comes mainly from finished-toothpaste extracts, skin-cell tests or model membranes rather than normal use in a human mouth. The honest point is that "milder" is a comparison of degree, not proof that a molecule cannot interact with living cells.
Why the mildness data does not transfer
The gentleness claims for these ingredients come from skin testing. The standard measurement is how much water escapes through skin afterwards, which is used as a sign that the skin barrier has been damaged.
That test only works if there is a barrier to damage. The lining of your mouth does not have one. A test of a structure your mouth does not possess cannot tell you what happens in your mouth.
The awkward example
Cocamidopropyl betaine is the replacement most often described as the gentle, coconut-derived one. It has also been named Allergen of the Year by the American Contact Dermatitis Society. That title goes to ingredients causing real, repeated allergic reactions.
The twist is that the trigger is usually not the molecule itself. It is the leftovers from how the molecule was made. So how cleanly a supplier works decides whether it causes reactions, and the ingredient name on the box cannot tell you that. Reactions in the mouth are documented too, including a case of inflamed lips traced by allergy testing to this ingredient in a toothpaste and mouthwash.
"Derived from coconut" describes a supply chain
Here is the cleanest illustration. Sodium lauryl sulfate is itself usually manufactured from coconut or palm kernel oil. A company could accurately print "coconut-derived" next to it.
What a molecule does to a cell membrane is set by its shape, its charge and how much of it is used. Not by which plant the carbon came from. A claim that rests on origin is not an argument about safety.
The question worth asking
- Someone who drops SLS to avoid irritation may land on an ingredient with a worse record of allergic reactions.
- Natural origin does not predict a low chance of allergy. It predicts nothing at all.
- Foam does not clean your teeth. Bristles do.
- Which means the real question is not which foaming agent is mildest, but whether the foam is earning its place. We make a toothpaste that does not foam, so weigh that framing accordingly.
Read the full evidence review The replacement surfactants one by one, the allergen record, and why skin mildness data does not transfer.
"SLS-free" has become one of the most reliable selling points in natural oral care. It is also one of the least informative, because removing sodium lauryl sulfate from a foaming toothpaste requires putting a different surfactant in. Whether that substitution is an improvement is a real question with a real answer, and the answer is not the one the label implies.
Key points
- A foaming toothpaste without SLS contains another surfactant. The common replacements are cocamidopropyl betaine, sodium cocoyl isethionate, sodium lauroyl sarcosinate and sugar esters such as decyl glucoside.
- Most safety data for these comes from dermatology, and skin irritation models measure damage to a keratinized barrier the oral mucosa does not have.
- Cocamidopropyl betaine, the most common "gentle" replacement, has been named Allergen of the Year by the American Contact Dermatitis Society, and oral reactions to it are documented.
- Sarcosinates are anionic surfactants, the same charge class as SLS.
- All of the listed replacements remain amphiphiles. At sufficient effective concentration, surfactants from every charge class can alter membrane permeability, reduce cell viability or solubilize the lipid bilayer; their potency is not equal.
- Direct oral-mucosa evidence is strongest for cocamidopropyl betaine. Evidence for the other substitutes comes mainly from oral-cell toothpaste extracts, skin keratinocytes, model membranes or irritation testing.
- "Derived from coconut" describes a feedstock, not a behavior. It says nothing about how a molecule interacts with a cell membrane.
What actually replaces SLS
Foam requires a surfactant. If a toothpaste foams and does not contain sodium lauryl sulfate, it contains something else doing the same job. The usual candidates:
| Ingredient | Charge class | Usually marketed as |
|---|---|---|
| Cocamidopropyl betaine | Amphoteric | Gentle, coconut-derived |
| Sodium cocoyl isethionate | Anionic | Mild, coconut-derived |
| Sodium lauroyl sarcosinate | Anionic | Natural alternative to SLS |
| Sodium cocoyl glutamate | Anionic | Amino acid derived |
| Decyl glucoside | Nonionic | Sugar-based, ultra mild |
None of this makes the replacements bad. Some are genuinely milder on several measures. The point is narrower: "SLS-free" describes the absence of one specific molecule, not the presence of gentleness, and the marketing consistently blurs those into each other.
How the replacements can still affect a cell
Changing the head group changes potency, but it does not remove the defining structure of a surfactant: a hydrophobic tail joined to a water-compatible head. The tail can partition into the phospholipid bilayer surrounding a cell. At lower effective concentrations, individual surfactant molecules can disturb lipid packing and barrier function. As the surfactant-to-lipid ratio rises, membrane lipids and proteins can be transferred into mixed micelles until the bilayer becomes permeable or is solubilized.
Cultured-cell experiments with several ionic and nonionic surfactants separate these effects. Loss of cell viability occurred below the critical micelle concentration, while outright cell lysis occurred near the bilayer-to-micelle transition. The amount needed varied substantially by surfactant, but in each case the cell membrane was the principal target.7 This is the shared mechanism that an "SLS-free" label does not remove.
| Replacement | What the evidence shows | Important limit |
|---|---|---|
| Cocamidopropyl betaine | A 2% solution caused significant electrical changes consistent with irritation after 15 minutes on human oral mucosa, although less than 2% SLS.8 Isolated-ingredient and toothpaste-extract experiments also found concentration- and time-dependent loss of viability in human gingival fibroblasts and an oral epithelial cell line.9,10 | These exposure conditions do not show that normal brushing causes tissue injury, and CAPB-containing toothpastes were less cytotoxic than SLS-containing toothpastes in one comparative laboratory study. |
| Sodium cocoyl isethionate | It retains an anionic head and fatty tail capable of interacting with proteins and lipids. Safety testing generally ranks it as milder than SLS, but irritation has still appeared under some higher or prolonged test exposures.11 | Direct oral-cell and normal-brushing evidence is sparse. It would be inaccurate to describe it as equally irritating as SLS. |
| Sodium lauroyl sarcosinate | An extract of a toothpaste containing this surfactant reduced human gingival-fibroblast viability in vitro, and the effect became smaller as the extract was diluted.12 | The experiment tested complete toothpaste formulations, so the effect cannot be assigned to sodium lauroyl sarcosinate alone. |
| Sodium cocoyl glutamate | In human keratinocytes it produced a concentration-dependent fall in cell viability, reaching 50% viability at a sufficiently high, prolonged exposure. It was nevertheless characterized as having relatively low cytotoxicity compared with the harsher control used in the study.13 | Those were skin-derived cells exposed for 24 hours, not oral mucosa during a two-minute brushing period. |
| Decyl glucoside | Experiments with phospholipid vesicles show that decyl alkylglucoside partitions into lipid bilayers. It is classed as a weak detergent because more accumulates in the membrane before the bilayer disintegrates. That does not mean disintegration is impossible.14 | A model membrane is not living oral tissue, and direct oral-cell evidence for decyl glucoside remains limited. |
Laboratory cell death is a hazard signal, not a demonstration of injury during normal use. Saliva dilutes and clears toothpaste, exposure is brief, and the complete formula can either increase or decrease the amount of free surfactant. Finished-product concentration, contact time and direct clinical testing matter more than the marketing category of the ingredient.
Why the skin data does not transfer
The mildness claims attached to these ingredients come overwhelmingly from dermatological testing, and the standard endpoint in that work is transepidermal water loss: how much water escapes through skin after exposure, used as a measure of barrier damage.
That endpoint depends on there being a barrier to damage. As covered in our article on surfactants and the oral mucosa, the lining mucosa of the mouth is non-keratinized and has no stratum corneum. A test measuring disruption of a structure the target tissue does not possess cannot be assumed to predict what happens in the target tissue.
This is not a claim that the replacements are secretly harsh in the mouth. It is a claim that the evidence usually cited for their mildness is about a different tissue, and that direct oral data is much thinner than the confidence of the marketing suggests. Recent in vitro work comparing the irritant potency of toothpaste ingredients on a common measure is the kind of study that begins to close that gap.1
The case of cocamidopropyl betaine
Cocamidopropyl betaine is the most instructive example, because it is the replacement most often described as the gentle, coconut-derived alternative, and it has the most documented problem.
It has been named Allergen of the Year by the American Contact Dermatitis Society, an honour reserved for ingredients causing clinically significant sensitization. The complication is that the sensitizer is generally understood not to be cocamidopropyl betaine itself but residual manufacturing intermediates, principally amidoamine and dimethylaminopropylamine.2 Purity of manufacture therefore determines allergenicity, which means the name on the label does not fully determine what is in the tube.
Reactions in the mouth are documented, not merely theoretical. A published case describes cheilitis, inflammation of the lips, traced by patch testing to cocamidopropyl betaine in a combined toothpaste and mouthwash.3 More broadly, toothpaste-induced contact stomatitis has been characterized in a case series and scoping review, establishing it as a recognized if uncommon clinical entity.4
The irony is worth stating directly. A consumer who switches to an SLS-free toothpaste to avoid irritation may be switching to an ingredient with a better-documented record of allergic contact reactions than the one they left behind. That is not an argument for SLS. It is an argument against treating a single absent ingredient as a proxy for safety.
"Derived from coconut" describes a supply chain
Sodium lauryl sulfate is itself typically manufactured from coconut or palm kernel oil. The lauryl chain in its name is a twelve-carbon chain, and coconut oil is a convenient source of twelve-carbon fatty acids. A product could accurately describe SLS as coconut-derived.
This is the clearest demonstration that feedstock and behavior are independent. What a molecule does at a membrane is determined by its structure, its charge, its critical micelle concentration and the concentration used, not by the plant its carbon chain came from. Any claim that rests on origin rather than on behavior is not making an argument about safety.
The same logic applies to the broader allergen literature, where reviews of established and emerging contact allergens in personal care products routinely include botanically derived ingredients alongside synthetic ones.5,6 Natural origin is not a predictor of low sensitization.
The honest position
Three things can be said with reasonable confidence.
First, sodium lauryl sulfate does interact with oral tissue in measurable ways, and the desquamation evidence for that is real. Second, replacement surfactants retain the physical ability to enter and disrupt lipid membranes, although their potency differs and direct oral evidence is uneven. Cocamidopropyl betaine has produced measurable oral irritation and oral-cell cytotoxicity under experimental conditions, while the evidence for several other replacements is indirect. Third, the evidence that foam improves cleaning is weak, because plaque removal is mechanical work done by bristles.
Those three together point at a different question than the one the category argues about. The interesting question is not which surfactant is mildest. It is whether a surfactant is earning its place in the formulation at all, and that is a question about what foam is for rather than about which foaming agent to choose.
We have an obvious interest in that framing, and readers should weigh it accordingly. It is also, as far as we can tell, where the evidence points.
References
- Kasi SR, Özcan M, et al. In vitro cytotoxicity (irritant potency) of toothpaste ingredients. PLoS One. 2025;20(1):e0318565. PMID 39883661.
- Jacob SE, Amini S. Cocamidopropyl betaine. Dermatitis. 2008;19(3):157-160. PMID 18627690.
- Agar N, Freeman S. Cheilitis caused by contact allergy to cocamidopropyl betaine in "2-in-1 toothpaste and mouthwash". Australasian Journal of Dermatology. 2005;46(1):15-17. PMID 15670171.
- Kalogirou EM, et al. Toothpaste-induced contact stomatitis: a retrospective study of 56 cases and scoping review. Journal of the American Dental Association. 2026. PMID 42138663.
- Smale NE, et al. Allergic contact dermatitis to personal care products: a focus on established and emerging allergens. Journal of the American Academy of Dermatology. 2026. PMID 42309282.
- Sukakul T, Svedman C. What is new in contact allergy to cosmetics for physicians, cosmetologists, and cosmetic users? Current Allergy and Asthma Reports. 2025;25(1):48. PMID 41134517.
- Partearroyo MA, Ostolaza H, Goñi FM, Barberá-Guillem E. Surfactant-induced cell toxicity and cell lysis: a study using B16 melanoma cells. Biochemical Pharmacology. 1990;40(6):1323-1328. PMID 2403386.
- Rantanen I, Nicander I, Jutila K, et al. Betaine reduces the irritating effect of sodium lauryl sulfate on human oral mucosa in vivo. Acta Odontologica Scandinavica. 2002;60(5):306-310. PMID 12418722.
- Tabatabaei MH, Sadeghi Mahounak F, Asgari N, Moradi Z. Cytotoxicity of the ingredients of commonly used toothpastes and mouthwashes on human gingival fibroblasts. Frontiers in Dentistry. 2019;16(6):450-457. PMID 33089246.
- Cvikl B, Lussi A, Gruber R. The in vitro impact of toothpaste extracts on cell viability. European Journal of Oral Sciences. 2015;123(3):179-185. PMID 25782087.
- Burnett CL, Heldreth B, Bergfeld WF, et al. Amended safety assessment of isethionate salts as used in cosmetics. International Journal of Toxicology. 2017;36(Suppl 1):5S-39S. DOI 10.1177/1091581816685552.
- Aydin N, Kiliç Süloğlu A, Idil N, Öztürk S, Karaoğlanoğlu S. Examination of cytotoxic and antimicrobial effect of whitening toothpastes: an in vitro study. Acta Odontologica Scandinavica. 2024;83:327-333. PMID 38801222.
- Kyadarkunte A, Patole M, Pokharkar V. In vitro cytotoxicity and phototoxicity assessment of acylglutamate surfactants using a human keratinocyte cell line. Cosmetics. 2014;1(3):159-170. DOI 10.3390/cosmetics1030159.
- Heerklotz H, Seelig J. Correlation of membrane/water partition coefficients of detergents with the critical micelle concentration. Biophysical Journal. 2000;78(5):2435-2440. PMID 10777739.
This article is educational and describes published research on surfactants as an ingredient class. It is not medical or dental advice, not a diagnosis, and not a claim about any product. If you suspect a reaction to an oral care product, a dentist or dermatologist can arrange patch testing, which is the only reliable way to identify the responsible ingredient.
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