Label Literacy

Why sodium benzoate is on MCAS avoid lists, and how skincare differs

It sits near the bottom of a lot of ingredient lists, including ours. Where the avoid lists came from, what changes when a preservative goes on skin instead of into a meal, and how to weigh the answer for yourself.

September 7, 2026 · Indiefog Naturals

You found the name. Then you found the list.

It goes the same way every time. You are reading an ingredient list, something unfamiliar catches your eye, and you search it. Somewhere in the results is a page telling you to avoid it if you have MCAS, or histamine intolerance, or a body that reacts to most things.

Now you are holding a bottle and a question, and the question has no obvious answer. The list gives you a name and a verdict. It does not give you the reasoning, and the reasoning is the part you need.

Sodium benzoate is the one that brings most people here, and it sits near the bottom of the list on several of ours. This page works through it properly. Where the avoid lists came from, what changes when a preservative goes on skin instead of into a meal, and what the evidence actually shows.

Why preservatives keep turning up on these lists

You will notice a pattern once you start looking. Preservatives appear on avoid lists more than almost any other category of ingredient, and there are three plain reasons for it.

They are meant to be biologically active. A preservative works by stopping organisms growing, so it is the one ingredient in a formula that has to do something to living cells. That makes it a reasonable place to look first.

They are almost everywhere. Anything containing water needs one, so a preservative is present in most of what anyone has ever reacted to. Presence in every suspect formula is weak evidence, and it reads as strong evidence.

And they are named. A reaction to a product with thirty ingredients gives you thirty suspects and no order to work through them in. The preservative is the one with a reputation attached, so it collects the blame that the other twenty nine also deserve a share of.

The alternative is worth stating plainly. A water-based product without a preservative becomes a microbiological problem within weeks on a warm shelf, and that is a considerably worse outcome for a reactive body than any preservative on any list.

Where avoid lists come from

They are not all the same kind of document. Knowing which kind you are reading tells you most of what you need.

None of these is wrong. They answer different questions, and a list from one category will be read as though it came from another unless you check.

The thing almost no list tells you

Here is the part worth carrying away from this page.

Most MCAS and histamine avoid lists were built for food. They are dietary documents. They were assembled to answer what happens when a substance is eaten, absorbed through the gut, and processed by enzymes in the gut wall and the liver.

Skin is a different route entirely. What crosses it, how much, how fast, and what it meets on the way are all different. A substance can matter a great deal in a meal and very little in a serum. The reverse also happens, and there are materials that do almost nothing when eaten and cause a visible reaction the moment they touch skin.

When a food list gets applied to a skincare label, that step is almost never named. The name matches, so the verdict carries across, and nobody checks whether the reasoning came with it.

This is not a reason to dismiss those lists. Many of the ingredients on them are worth avoiding on skin as well, sometimes for the reason given and sometimes for a different one. It is a reason to ask which document you are reading before you act on it.

Four questions to ask of any list

When you are tired, which is most of the time, these are the four that do the work.

Every preservative costs something

There is no option that carries nothing. Here is what the realistic choices actually bring with them, so you can see the shape of the decision any brand is making.

That last row is the one to remember. If a preservative is the thing you would rather avoid, the reliable answer is a product with no water in it. That is a formulation fact rather than a brand claim, and it holds no matter whose bottle you are holding.

The word alcohol, which tells you almost nothing

Benzyl alcohol is the one that stops people, and usually for the wrong reason. The word is doing work it should not be trusted with. Three unrelated families of ingredient carry it, and they behave nothing alike.

So a label reading cetearyl alcohol is telling you something soft. A label reading alcohol denat. near the top of a list is telling you something else entirely. Reading for the family rather than the word is the same habit as reading for the Latin.

Alcohol is not the only word that behaves this way, and we will use one of our own as the example. The Cloud Cleansing Powder contains sodium lauryl sulfoacetate, usually shortened to SLSA. That sits a few letters from sodium lauryl sulfate, or SLS, which appears on more avoid lists than almost any other ingredient. They are different molecules in different chemical classes. One is a sulfate ester. The other carries its sulfonate group on an acetate bridge, which is a different arrangement with a similar name. SLSA is the material most often chosen when a formula is built to be sulfate-free.

Whether that difference matters on your skin is a question for a patch test rather than for a name. We are naming it here because you would find it yourself, and because a brand that lets you find it is telling you something about how it handles the rest of the list.

The worked example · sodium benzoate

We use it, so we will run our own ingredient through the method rather than someone else's.

Sodium benzoate sits near the bottom of the list on three of our essences, three of our serums, and two of our cleansing bars. On MCAS and histamine avoid lists it is usually described as a histamine liberator, meaning a substance that prompts the body to release histamine of its own.

Question one, eating or applying. Those lists are dietary. Sodium benzoate is a common food preservative, which is the context the entry was written in. The skincare verdict arrived by name-matching.

Question three, established or named. The histamine liberator category rests mostly on laboratory and animal work, some of it from the 1950s and 60s, and on lists compiled inside patient communities and copied between them. We went looking for a clinical study in people showing that sodium benzoate applied to skin triggers mast cell activation. We did not find one. If you know of one, send it to us. We will read it, and if it changes this page we will change this page.

And then the part the lists leave out. There is a real, documented effect here. It is a different one, and it is better evidenced than the thing being claimed.

In an acidic formula, a portion of sodium benzoate exists as benzoic acid. Benzoic acid is one of the classic causes of non-immunologic contact urticaria, an immediate reaction on the skin it touches. No prior exposure is required, so a first application can produce it.

Question two, concentration. The effect is dose-dependent, and the acidity of the formula changes how much of the benzoate is present as the acid at any moment. The European Union caps benzoic acid and its salts at 0.5% in leave-on products. The Cosmetic Ingredient Review panel assessed the same studies and concluded these reactions are not a concern at the concentrations cosmetics actually use.

So the honest summary is this. The mechanism the lists name has not been shown in people. A different mechanism has been, it is dose-dependent, and the bodies whose job it is to weigh that have looked at it and set a limit rather than a ban.

You now know more about this ingredient than the list told you, and you are in a position to decide rather than to comply.

How to find out on your own skin

None of the above beats testing it on your own skin. Two things decide whether a patch test tells you anything. Where you put it, and when you look.

When your skin is already reacting

All of the above assumes a settled starting point. A lot of the time there is not one.

When your system is already loud, the same product can read differently than it did last month. A formula you have used for a year can sting on a Tuesday. That is your capacity changing rather than the formula changing, and it is worth naming, because it makes an ingredient list hardest to interpret exactly when you most want an answer from one.

Our advice in that state is the advice a careful elimination approach gives you with food. Simplify and remove. Go down to the fewest inputs you can manage, hold there until things quiet, then add back one at a time.

The reasoning carries across from the plate to the shelf. A short list is easier to learn from. Fewer ingredients means fewer suspects if something goes wrong, and a system with nothing spare is the worst possible place to run a thirty-suspect investigation.

So when we are asked what to use while things are loud, we point at the shortest lists we make rather than at anything clever. The Cloud Cleansing Powder at eight ingredients, the Soothe Face Butter at twelve, and the Glow Elixir at nine if it is tolerated. None of the three contains water, so none of them carries a preservative of any kind, and the lists stay short enough to work through if something does go wrong.

Then add back one product at a time, and only once the last one has been quiet for a while. This is slow. It is the only version that leaves you with an answer you can still use next year.

None of this is a treatment plan, and it belongs alongside your doctors rather than instead of them. It is a way of giving your skin less to sort through while your system does its own work.

What we do about it

We use gluconolactone and sodium benzoate in our water-based formulas. It is ECOCERT-certified, at 2.00% of the finished formula in the serums and the Clarity Essence, and 1.00% in the Harmony Essence. Sodium benzoate is 22 to 28% of that material, which puts it well under half a percent of what is in your hand, and under the European ceiling.

We chose it over a benzyl alcohol system because benzyl alcohol is a declarable fragrance allergen, and its absence is the entire reason those formulas can say fragrance-free with nothing attached to it. That was the trade. A preservative carrying a fragrance allergen, or one carrying a documented contact urticant. Nothing on the table carried neither.

That decision follows a rule we are not required to follow. Benzyl alcohol is second on the European Union's list of 26 fragrance allergens, which must be declared as allergens above 0.001% in a leave-on product. The United States has no equivalent requirement. The Modernization of Cosmetics Regulation Act directed the FDA to write one, and as of 2026 it has not been issued.

We hold to the European standard anyway. It is why the products that contain benzyl alcohol are labelled unscented and never fragrance-free, and why we name benzyl alcohol as the reason rather than leaving you to work it out. The American rule would let us say less. We would rather you had the European label.

If you would rather avoid it, most of our line is already without it.

That middle row matters, so we will say it rather than let you find it. The cream, the balm and the magnesium butters contain no sodium benzoate. They contain benzyl alcohol instead, which is why they are labelled unscented rather than fragrance-free. Moving from one to the other trades one question for a different question.

The bottom row is the group with neither. Those formulas have no water, so they need no preservation at all, and that is a decision about format rather than a claim about safety.

We are looking at whether a system exists that clears the same bar without either compromise. We have not found one we would put in front of you. If we do, we will say so plainly, run the testing that proves it holds, and change the label. What we will not do is swap one ingredient for another and describe it as an improvement without naming what the new one costs.

The short version

Check which kind of list you are reading. Check whether it was written about food. Check whether it gives you a concentration. Check whether the mechanism has been shown in people, or only named. Then patch test, look early, and keep your own record, because the list is about a substance and your record is about you.

Every ingredient we leave out is left out on purpose, and the ones we keep are in on purpose too. Both halves come with reasons, and you should be able to read them.