3-free to 21-free: what the "free" numbers really mean

Walk through any polish aisle online and the numbers come at you fast: 3-free, 5-free, 10-free, 16-free, 21-free. It reads like a scoreboard, and the obvious assumption is that bigger means better. The truth is more interesting and a lot more useful, because once you can read the labels, you can decide what you actually care about instead of paying for the biggest number.

Where the numbers came from

The counting convention started with the original three ingredients of concern, the so-called toxic trio that built nail polish's old reputation:

• Formaldehyde, a hardener and preservative, classified as a known human carcinogen at meaningful exposure levels
• Toluene, a solvent with neurotoxicity concerns
• DBP (dibutyl phthalate), a plasticizer flagged as an endocrine disruptor

A polish formulated without all three is 3-free. Most of the mainstream industry crossed that line years ago, so 3-free is closer to a baseline than a badge.

From there, brands kept counting. Each higher number adds more excluded ingredients. Commonly:

• 5-free typically adds formaldehyde resin (a common contact allergen) and camphor
• 7-free often adds ethyl tosylamide (restricted in EU cosmetics) and xylene
• 10-free usually adds some mix of parabens, fragrance, and animal-derived ingredients
• 12-free and up extend into solvents and other additions, and at the high end the lists start including ingredients that were rarely in polish to begin with

The honest caveat: there is no referee

Here is the thing the marketing does not say out loud: no regulator or independent body defines what 10-free means. Each brand writes its own exclusion list, so one brand's 10-free is not necessarily another's. The low numbers are fairly consistent across the industry; past ten, you have to read the actual list. That is not a scandal, but it is a reason to treat the number as a shorthand rather than a certification.

The same goes for the words next to the numbers. Non-toxic and clean are not regulated terms in cosmetics. In the US, the FDA does not define them, and it does not approve cosmetics before sale at all; safety responsibility sits with manufacturers. A "non-toxic" label tells you about a brand's positioning; the ingredient list tells you about the polish.

The labels that mean something different

A few terms get mixed into the free-number soup but describe entirely different things:

• Vegan means no animal-derived ingredients: no carmine (a red pigment from insects), no guanine (shimmer from fish scales), no beeswax. A polish can be vegan and still be a completely conventional petrochemical formula.
• Cruelty-free is about animal testing, not ingredients. Vegan and cruelty-free do not imply each other.
• Plant-based is a positive sourcing claim: key components derived from plants like cassava, corn, or sugarcane. All plant-based polishes are vegan; most vegan polishes are not plant-based.

Knowing the difference means you can stack the claims that matter to you instead of assuming one implies another.

So which level should you pick?

There is no universally right answer, which is exactly why the labels exist. A practical way to think about it:

• You just want modern polish: 3-free is effectively the industry floor. You likely already own it.
• You have sensitive skin or allergy history: 5-free and up starts excluding the common contact allergens like formaldehyde resin. If your concern is gel polish allergens specifically, that is a different ingredient family entirely; read our HEMA guide.
• You are pregnant or planning: many people choose 3-free as a sensible baseline and stop worrying. Our pregnancy and polish guide covers what the evidence actually says.
• You want maximum exclusion for its own sake: the high-number and plant-based formulas exist for you, with the caveat that past ten, you are comparing brand-specific lists.
• Your priority is ethical, not chemical: vegan and cruelty-free are your labels, independent of any free number.

How Polish Index handles all of this

We track brand-stated certifications on every polish in the Polish Index™ catalog and turn them into filters, so the label reading is already done. Start at the Clean Beauty hub and browse by 10-Free, Vegan, Plant-Based, Cruelty-Free, and more, alone or combined.

Two honesty notes, because trust is the whole point of this section. First, these are brand-reported claims; nobody independently lab-tests every polish on the market, including us. Second, brands reformulate, so if an ingredient matters to you medically, the label on the bottle in your hand is the final word. What we promise is that our data reflects what brands publish, and that when it changes, we update.

The free numbers are not a scoreboard. They are a menu. Decide what you care about, pick your level, and then get back to the fun part: choosing colors.

Sources

• FDA: Nail Care Products
• FDA: Shelf Life and Expiration Dating of Cosmetics
• MotherToBaby: nail treatment safety in pregnancy
• Allergic contact dermatitis to toluene-sulfonamide-formaldehyde resin (PMC, 2024)