How to read an ingredient label

Almost nobody is taught how to read an ingredient list, which is strange, because it is one of the few pieces of writing that is legally obliged to be true.

It is not obliged to be clear. That is a different thing, and it is the gap this guide is about.

Rule one: the order is the quantity

Ingredients are listed in descending order by weight. The first ingredient is the largest part of what you are holding, the last is the smallest. This holds for food and for cosmetics.

This one rule does more work than any app, any score and any front-of-pack claim. A cereal whose second ingredient is sugar is a sugar product with cereal in it. A serum whose marketed hero ingredient appears last is selling you the idea of that ingredient.

Rule two: below one percent, the order stops meaning anything

In cosmetics, ingredients present at one percent or less may be listed in any order after the ones above one percent. Under EU rules this is set out in the Cosmetic Products Regulation.

This matters more than it sounds. Most cosmetic actives are used at fractions of a percent. Retinol is. Preservatives like Potassium sorbate are. So the entire back half of a cosmetic ingredient list is unordered, and reading meaning into the sequence there is reading noise.

Practically: find where the list stops looking like a formula and starts looking like a list of scientific names, and treat everything from roughly that point on as “present in small amounts, in no particular order.”

Rule three: some words are legal terms, and some are marketing

This is where most of the confusion lives, because both kinds of word appear in the same typeface.

Legal terms. “Parfum” or “Fragrance” is a permitted collective term, which is why a single word can stand in for dozens of components. In the EU, specific fragrance allergens have to be named separately once they exceed set thresholds, and that list of named allergens was significantly expanded in 2023, which is why fragranced products have been growing longer ingredient lists. In US food labelling, “natural flavors” is a defined term with an actual regulatory definition in 21 CFR 101.22, and that definition is about the origin of the flavouring, not about it being simple, minimal or good for you.

Marketing terms. “Clean”, “non-toxic”, “chemical-free” and, in most contexts, “natural” on the front of a pack are not defined terms. They constrain the manufacturer roughly not at all. A front label saying “no nasties” and a back label containing exactly the same preservative as the competitor is an extremely common combination, and it is not illegal, because “nasties” means nothing.

The useful habit is to treat the front of the pack as an advertisement and the back as the document.

Rule four: allergens cannot hide

This is the part of the label with the sharpest teeth, and the part worth trusting most.

In the United States, the major food allergens must be declared plainly. There are nine of them: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans, and sesame, which became the ninth under the FASTER Act with effect from 1 January 2023. In the EU, the equivalent allergens have to be emphasised within the ingredient list itself, usually in bold.

So an ingredient list will not conceal a declared allergen behind a technical name. What it will not tell you is what happened in the factory.

Cosmetic names versus food names

The same substance has two vocabularies. Cosmetics use INCI names, an international naming system, which is why water appears as “Aqua” and vitamin E as “Tocopherol”. Food in Europe additionally uses E numbers for approved additives, which are identifiers rather than warnings: E202 is Potassium sorbate, and the number tells you it has been assessed and approved, not that it is suspect.

The reason ingredient lists look intimidating is largely that they are written in a naming system designed for regulators and formulators, which is precisely the problem Pura was built for.

What to actually do with all this

Four questions, in order, get you most of the way:

1. What are the first three ingredients? That is most of the product.
2. Where does the thing on the front of the pack appear in the list?
3. Is anything here on my own list, for my own reasons?
4. Is the claim on the front the kind of word that means something?

The third question is the one that changes by person, and it is the one no universal score can answer. What matters if you are pregnant is different from what matters if your skin reacts to everything, and neither is captured by a number out of a hundred.