For almost 90 years, toothpaste manufacturers have been incorporating a synthetic detergent called sodium lauryl sulfate (SLS) into their formulas, with one devastating side effect: it ruins your ability to taste after brushing.
The effect has been understood by the oral care industry for decades. Yet, as appreciation of coffee, food, and wine has evolved into an important part of our lifestyles, the toothpaste we use twice daily has remained unchanged and unquestioned.
It was certainly something I’d misunderstood. Until one morning at work, when everything I tasted seemed wrong.
For 15 years, I poured my life into creating great coffee as the founder of Redbrick Coffee.
My team and I obsessed over the coffees we sourced from different origins, the roast profiles we developed, the grinders and coffee machines we worked with, the water we brewed with, and the recipes we followed for extraction.
We worked endlessly, searching for that magical balance between sweetness, acidity and bitterness that makes coffee the drink we love so much.
For us and anyone working in specialty coffee, taste wasn’t just simply a pleasure. It was a professional tool. The ability to recognise subtle differences in flavour was central to the work, whether we were buying green (raw) coffee from origin, roasting, brewing or serving it.
Every morning, our team would cup (taste) small samples of the previous day's production roasts as part of our quality control.
On this particular morning, everything tasted wrong to me. The coffees were sour, bitter, unbalanced and unpleasant.
After working my way through the samples, I finally stopped and questioned the team. Had something happened to the roasting? Why did all the coffees taste so terrible?
The response was confusing. To everyone else, the coffees tasted exactly as they should. Nothing seemed out of place.
As we tried to make sense of it, one of our team members, a chemical engineer, asked a rather unexpected question.
What toothpaste had I brushed my teeth with that morning? Was it different from what I normally used?
Unknowingly, I'd used a conventional toothpaste containing sodium lauryl sulphate (SLS) which had completely changed how I experience taste that morning.
For someone who had spent years obsessing over every variable affecting the flavour of coffee, the discovery sent me down an entirely new rabbit hole.
Why does toothpaste contain an ingredient that affects our taste so badly and does it have to?
To find the answers I started to dig into the history of toothpaste.
A curious discovery from 1962
In April 1962, three researchers working for Lever Brothers, the company behind Pepsodent, filed a patent for a new type of toothpaste detergent.
The document contains a remarkable observation.
Certain commonly used toothpaste detergents, including sodium lauryl sulphate, were known to produce what the researchers called the orange juice effect, an unpleasant change in flavour when someone drank citrus juice after brushing.
More interestingly, they were trying to do something about it.
The patent describes alternative surfactants and experiments in which participants brushed their teeth, waited five minutes and then tasted orange juice. The researchers compared the acceptability of the flavour afterwards, while also measuring how well the different formulations foamed.
They weren't questioning whether toothpaste needed a surfactant. They were looking for one that could do its job without interfering so noticeably with taste.
In one small comparison, all eight panellists rated the orange juice experience after using the SLS formulation as unacceptable. Several alternatives performed substantially better.
This was 1962. More than six decades ago.
The experiments were small, but the significance was clear. Researchers within the oral care industry had recognised the problem and were actively investigating alternatives.
And yet, SLS remained one of the most widely used ingredients in toothpaste. Why?
Ninety years of foam
The answer begins in the 1930s, when synthetic detergents offered toothpaste manufacturers an alternative to traditional soaps.
In 1937, Pepsodent introduced a formulation containing sodium alkyl sulphate, marketed under the name Irium. It belonged to the same broader family of surfactants as SLS.
Surfactants serve a useful purpose. They help water spread across teeth and disperse particles. SLS offered manufacturers an effective, inexpensive, and readily available ingredient that produced the generous lather consumers had come to associate with cleaning (not just in toothpaste, but for many household products).
But the evidence of its effect on taste continued to develop.
In 1980, researchers John DeSimone, Gerard Heck and Linda Bartoshuk published a study in the scientific journal Chemical Senses examining how SLS alters our perception of taste. Their experiments demonstrated that SLS reduced the perceived intensity of sweetness while increasing bitterness.
Yet SLS remained widely used.
Cost, availability, performance in formulations and consumer association with foam all help explain its continued use.
The problem wasn't unknown. Taste just wasn't the focus.
Meanwhile, our appreciation of taste has evolved.
Our appreciation of coffee, food, and wine has changed enormously.
We talk about origins, varieties, brew methods, acidity and balance. We care about ingredients, preparation, and the subtle differences that make something worth experiencing.
We spend more time, money, and attention than ever pursuing great taste experiences.
Yet for all the attention we give to taste, most of us have never been told why toothpaste actually spoils the experience of what comes next, let alone that it doesn't have to be that way.
Someone approaching oral care from a toothpaste formulation background naturally thinks about cleaning and performance.
Someone approaching it from specialty coffee might start with a different question. What happens to taste?
Why can't we have both, clean teeth and good taste?
Surfactants have a legitimate role in toothpaste, it's just that SLS isn't the only option. Alternatives have existed for decades, offering different cleaning, foaming and sensory characteristics.
That doesn't mean every SLS-free toothpaste will preserve taste equally. The whole formulation matters.
But it does mean that effective oral care and consideration for what we taste afterwards don’t need to be competing ambitions.
It's time our expectations of toothpaste caught up with our appreciation of taste.
1. Cahn, A., Konort, M. D., Goldberg, M. A. (1966). Dentifrice composition. US Patent No. 3,256,155. Lever Brothers Company. Filed 11 April 1962. https://patents.google.com/patent/US3256155A
2. DeSimone, J. A., Heck, G. L., Bartoshuk, L. M. (1980). Surface active taste modifiers: A comparison of the physical and psychophysical properties of gymnemic acid and sodium lauryl sulfate. Chemical Senses, 5(4), 317–330.