Thirty out of a hundred.

That is what the Yuka app gives Salt of the Earth's Crystal Deodorant Classic. A product sold as natural, unscented, one ingredient, about as clean as a deodorant is supposed to get. I scanned it myself in October 2026, along with two of their sprays. They came back 30, 49 and 49. All three sit in Yuka's poor band.

Then I scanned ours, expecting to have to be diplomatic about the result. Lifelong came back 93. Excellent.

I run Lifelong, so weigh that however you like. But I did not build the app, I do not pay it, and I could not have moved the number if I had wanted to. Here are the four scans.

93/100 Excellent
Lifelong refillable deodorant49/100 Poor
Salt of the Earth Natural Spray49/100 Poor
Salt of the Earth Effective Natural30/100 Poor
Salt of the Earth Crystal Classic

Yuka scans a barcode and rates a product out of 100 on its ingredients alone. Nothing else. No brand pays to appear in it. Above 75 is excellent, 50 to 74 is good, anything under 50 is poor.

One ingredient explains the entire gap: potassium alum. It is the only thing Yuka flags in any of the three. Every other ingredient on those labels comes back risk-free. The crystal scores worst for the simplest reason there is. Alum is the only thing in it. There is nothing else in the bottle to soften the score.

And enough people worked this out for themselves that the company had to answer for it in public. Salt of the Earth published a post on its own site that opens: "We've noticed some concerns from our customers after using the Yuka app to scan our Salt of the Earth deodorant products." When a brand writes a public reply to a scanning app, the app has already won that argument in its customers' heads.

Now pick up the spray bottle. The front says "100% Natural Origin". That is completely true. Potassium alum is a mineral, dug out of the ground. It is also an aluminium salt, and it is the one thing on that label Yuka marks as a risk. Natural origin and aluminium-free are two different claims. Only one of them is printed on that bottle.

Their defence is that Yuka does not account for certifications like COSMOS. True, and beside the point. COSMOS certifies where an ingredient came from, not whether it is in there. A mineral out of the ground is natural. It still contains aluminium.

I am not telling you alum is dangerous. Yuka calls it a moderate risk, that is Yuka's word, and I am not going to inflate it. The point is narrower and harder to argue with: if you bought that bottle to get away from aluminium, you did not get away from aluminium.

I run Lifelong, a refillable deodorant brand, so you should weigh what follows accordingly. I have tried to keep to what the labels and the sources actually say, and I link each claim to where it came from. This is about what words on a label mean, not a safety warning. For that question, see our look at whether aluminium in deodorant is safe.

Is Salt of the Earth deodorant aluminium free?

Not across the board, and that is the honest answer. The brand sells several formats, and they are built differently. Here is how it breaks down from its own product pages:

• Roll-on: the Lavender & Vanilla roll-on lists Potassium Alum as its second ingredient after water. The unscented roll-on uses the same wording.
• Crystal: the Crystal Deodorant Classic has one ingredient, Potassium Alum.
• Spray: retailer listings for the spray also show Potassium Alum. I could not load the brand's own spray page, so check the pack in your hand.
• Sticks and balms: formulated without potassium alum. Most listings use bicarbonate of soda instead, and some use magnesium hydroxide.

So "does Salt of the Earth contain aluminium?" has no single answer. If you buy the stick, the aluminium question mostly goes away (the bicarbonate question may not). If you buy the roll-on or the crystal, the aluminium is there by design.

What is potassium alum, and why does a mineral salt contain aluminium?

PubChem lists potassium alum under its chemical name, aluminum potassium sulfate dodecahydrate. In plain terms, it is a double sulfate salt: potassium and aluminium locked into the same crystal with sulfate and water. Salt of the Earth's own explainer on how alum works gives the full name as potassium aluminium sulfate. Nobody is hiding that.

"Natural" and "contains aluminium" are not opposites. The brand describes its alum stone as a naturally occurring mineral salt, and I have no reason to doubt it. But "mineral" describes where an ingredient comes from. It does not tell you what is in it. Plenty of minerals contain aluminium.

How alum differs from antiperspirant aluminium

This is where people understandably get confused, so I will be careful. Potassium alum and the aluminium chlorohydrate used in antiperspirants are different compounds. PubChem gives potassium alum as a sulfate salt; it gives aluminum chlorohydrate as a chloride-and-hydroxide compound with a different formula entirely. They are not the same chemical wearing two names.

They are also described as doing different jobs. Antiperspirant research, such as a 2017 Soft Matter study by L'Oréal, CNRS and ESRF researchers, points to aluminium polycations aggregating sweat proteins into a plug inside the duct. Salt of the Earth says its alum is made of particles "too large to pass through your skin", sits on the surface, does not block sweat and acts on odour-causing bacteria instead.

Here is the limit of what I can tell you. That account of alum comes from the brand, and at least one other natural deodorant brand says much the same of its own alum. I did not find independent testing of potassium alum that settles it either way, and the Soft Matter work is about antiperspirant-type polycations, not alum. So "different compounds" is solid. "Behaves completely differently on skin" rests on the manufacturers' account. Salt of the Earth itself says alum gives "a mild astringent feel for drier underarms", so it is not inert.

Side by side: what is actually on each label

Two things stand out. No single "yes or no" covers Salt of the Earth, because the answer changes by format. And nobody in this table is perfectly simple: fragrance is listed on every row except the alum crystal, ours included.

What "natural" on a label does and does not tell you

Certifications like COSMOS Natural tell you about an ingredient's origin and how a product is made and sourced. They are useful, and they take real effort to earn. What they do not do is promise the absence of every ingredient a given shopper wants to avoid. Salt of the Earth's alum sprays and roll-ons carry COSMOS Natural certification, so the standard evidently allows potassium alum. The brand says its crystal range sits outside COSMOS, being a single mineral.

That is the gap this article is about. A shopper who sees "natural" and "certified" on the front of a pack reasonably assumes "no aluminium". The brand has not said that, and its product pages show the alum plainly. But the assumption is easy to make, and it is exactly why reading the ingredient list beats trusting the headline claim, whoever makes the product. To its credit, the brand is explicit about this in its own words: "Our sprays, roll-ons and crystals contain potassium alum, a mineral salt that contains aluminium. It isn't the aluminium chlorohydrate used in antiperspirants, but it is an aluminium salt, so we don't call those products aluminium-free."

Two different things people mean by "aluminium-free"

When someone searches for an aluminium-free deodorant, they usually mean one of two things, and the phrase gets used loosely.

1. No antiperspirant-type aluminium salts. This is the common meaning. The person wants to avoid aluminium chlorohydrate or aluminium zirconium compounds, the sweat-blocking actives. Under this reading, potassium alum is a grey area: it is not that kind of salt, but it is an aluminium compound.
2. No aluminium-containing ingredient at all. The person reads the full ingredient list and wants none. Under this reading, potassium alum fails, because it is potassium aluminium sulfate.

Neither reading is wrong. They just answer different questions. I covered the first in our guide to reading the label on aluminium-free products. If you are in the second camp, the ingredient list is the only reliable guide, and the front of the pack is not.

What Salt of the Earth does well

It would be unfair to read all this as a mark against the brand, because on several counts it does things properly. Its deodorants are certified COSMOS Natural by the Soil Association, and it holds Vegan Society and Leaping Bunny approval. It publishes its ingredients, including the alum, on the product page. And it offers genuine alternatives: if you want to avoid alum, the stick is built without it.

It has also addressed the concern directly. In a post on its product ratings, Salt of the Earth says it noticed "some concerns from our customers" after they scanned its deodorants with the Yuka app. It describes Yuka as not swayed by brands, then argues that Yuka's criteria may not fully capture standards such as COSMOS certification. What I can say is that the brand has acknowledged the question publicly and explained its position, which is more than many do.

Where Lifelong fits, and where it does not

Our refill formula uses arrowroot and zinc oxide. It contains no aluminium salts and no sodium bicarbonate, which is why we keep an eye on the baking soda irritation question when people ask us about stings and rashes. It is a natural deodorant, not an antiperspirant: it is there for odour and will not stop you sweating, and the same is true of the alum products above on their makers' own account.

One distinction I want to be precise about. The Luxe applicator is anodised aluminium, which is why it lasts. That is the case you hold, and the formula inside it has no aluminium in it. The Luxe is £49, Vibes (recycled ocean-bound plastic) is £14.99, and a refill is £8.99 and lasts about 8 weeks.

Fairness cuts both ways. A product free of aluminium and bicarbonate is not automatically right for you. Scented refills carry perfume, as the table shows, and anyone with a known fragrance sensitivity should patch test whatever they buy. If you are comparing options, our round-up of the best aluminium-free deodorants in the UK sets several of them out side by side.

How to check any deodorant label in 60 seconds

• Read the ingredient list, not the front of the pack. Look for "Potassium Alum", "Aluminium", "Aluminum" or "Alum".
• Decide which meaning of "aluminium-free" you are after, and check the label against that one.
• Look for sodium bicarbonate if you have reacted to natural deodorants before.
• Check the allergen declarations at the end of the list if fragrance bothers you.
• Remember that the format matters: the same brand can sell products with different formulas.

If your skin reacts, stop using it and speak to a pharmacist or GP. I am not a doctor or dermatologist, and nothing here is medical advice.

Frequently Asked Questions

Is Salt of the Earth deodorant aluminium free?

Not every format. The roll-on, spray and crystal list potassium alum, which is potassium aluminium sulfate and does contain aluminium. The sticks and balms are made without potassium alum. Check the ingredient list on the specific product.

Does Salt of the Earth crystal deodorant contain aluminium?

Yes. The Crystal Deodorant Classic has a single ingredient, potassium alum, which the brand describes as a naturally occurring mineral salt. Chemically it is potassium aluminium sulfate, so it contains aluminium. That is stated openly on the product page.

Is potassium alum the same as the aluminium in antiperspirant?

No. Potassium alum is a sulfate salt, while antiperspirants use compounds such as aluminium chlorohydrate. Brands say alum stays on the skin's surface and does not block sweat ducts. I found no independent testing of alum to confirm that, so treat it as the manufacturers' account.

Why did my Yuka scan flag my natural deodorant?

On Salt of the Earth's alum products the flag is potassium alum, which Yuka rates as moderate risk. Scanning them in October 2026, the Crystal Deodorant Classic scored 30 out of 100 and both the Natural Spray and the Effective Natural Deodorant scored 49, all inside Yuka's poor band, with every other ingredient marked risk-free. For comparison, Lifelong's refillable deodorant scored 93. Salt of the Earth argues Yuka's criteria do not capture certifications like COSMOS. Open the app's own breakdown to see what it flagged on your pack.

Does Salt of the Earth deodorant contain baking soda?

It depends on the product. Most stick listings use bicarbonate of soda, though some use magnesium hydroxide. The current Lavender and Vanilla roll-on and the crystal do not list it. Some retailer spray listings do, so read the label on your pack.

Is Salt of the Earth deodorant an antiperspirant?

No. On the brand's own account, its alum deodorants do not block sweat. They are designed to tackle odour. The roll-on page describes alum as giving a mild astringent feel for drier underarms, which is different from stopping sweat.

Is Lifelong deodorant aluminium free?

The refill formula contains no aluminium salts and no sodium bicarbonate. It uses arrowroot and zinc oxide. The Luxe applicator is made of anodised aluminium, but that is the case, not an ingredient. Lifelong is a natural deodorant and does not stop sweat.