The nano marker is one of the few pieces of genuinely precise information on a sunscreen pack, and it is routinely read as the opposite of what it is. It is a disclosure requirement. It exists so that a consumer can know what is in a product, not so that a consumer can avoid something a regulator considers dangerous.
The definition
Cosmetics law defines a nanomaterial for its own purposes. The definition has three limbs, and all three matter.
- Insoluble or biopersistent. A material that dissolves is not a nanomaterial for this purpose, because it does not persist as a particle. This is why fine particle metal oxides are in scope and many other small things are not.
- Intentionally manufactured. Incidental fine material generated in processing is treated differently from material deliberately made at that scale.
- One or more external dimensions in the defined size range, conventionally around one to one hundred nanometres. Note the phrasing: one dimension is enough, so a plate or a rod with one small dimension qualifies.
The definition has been refined over time to address exactly the problem raised in particle size: that powders have distributions rather than sizes. Refinements have addressed the proportion of particles within the size range and how aggregates and agglomerates are treated. Anyone relying on the term should read the current text rather than a summary, including this one.
What the marker requires
Where a nanomaterial is present, the ingredient list must identify it, with the word nano in brackets following the ingredient name. So a pack may read zinc oxide in one product and zinc oxide followed by the nano marker in another. Both are lawful. Both use a permitted filter. The marker tells you that the material falls within the defined size criteria, and nothing more.
Nanomaterial forms of the two metal oxides also have their own entries on the permitted filter annex, with conditions attached. Those conditions concern the characteristics of the material, its purity, its surface treatment and its photocatalytic activity, and the applications for which it may be used. In particular, assessment work advised against uses that could lead to inhalation, which is why sprayable and loose powder forms are handled differently.
This sunscreen is non nano, so the particles are too large to enter the skin
- What would have to be true
- That non nano is a defined product characteristic with a verifiable threshold.
- That the size boundary used for labelling corresponds to the boundary at which skin penetration begins.
- What is established
- The nanomaterial definition and the labelling requirement exist in cosmetics law, and any nanomaterial present must be identified in the ingredient list.
- Studies of both conventional and nanoscale metal oxide filters on intact skin have reported penetration limited to the outer dead layers and to follicular openings.
- What is not established
- That non nano has any legal definition, threshold or verification requirement. It does not appear in cosmetics law at all.
- That the labelling size range was derived from a threshold for dermal penetration. It was not.
What non nano actually is
It is a claim a company makes on its own authority, on the basis of a specification from its raw material supplier. That specification is likely to be genuine. It says that the bulk of the particle size distribution of the grade supplied sits above the threshold. It cannot say that no particles below the threshold are present, and a company making the claim would not normally assert that.
There is no requirement to substantiate the term to a regulator before use, because the term does not exist in cosmetics law. It falls instead under advertising rules, which require that claims are capable of objective substantiation and are not misleading. A non nano claim that implies a safety advantage over a nano labelled product is, on the current state of the evidence, doing exactly what those rules are designed to catch.
Why the disclosure rule exists at all
Because nanoscale materials as a class raised questions that could not be answered by extrapolating from bulk material, and because policymakers took the view that consumers should be able to see when they are present. That is a reasonable position and it does not imply a finding of harm. A great many disclosure requirements in consumer law exist for informational rather than protective reasons.
Alongside disclosure, the regulation requires notification of products containing nanomaterials, so that authorities know what is on the market and can act if evidence changes. That is the mechanism doing the protective work, and it is invisible to the shopper.
What a reader can reasonably do with this
Read the ingredient list. If the marker is there, you know the formulator chose fine particles, which usually means the product will be less visible on skin and may have needed more dispersion engineering. If the marker is absent, you know the material supplied was specified above the threshold, which usually means a whiter finish.
That is a texture and appearance signal, and it is a reasonable one to act on. Treating it as a safety signal requires evidence that is not there, in either direction. The safety questions that genuinely remain open are set out in the nanoparticle safety questions, and the position is that dermal application to intact skin has been examined repeatedly, while inhalation and environmental fate are where the live questions sit.
Products marketed as natural are more likely to advertise non nano and more likely to use coarser grades, which means they are more likely to be visibly white, which means they are more likely to be applied thinly. The chain from a marketing claim to a reduction in delivered protection is short and is rarely drawn.
Where the assessments are careful
Assessment work on dermal application has consistently qualified its conclusions with the phrase healthy, intact skin. That qualification is doing real work. Penetration through skin that is broken, sunburnt, or affected by a condition that disrupts the barrier has been studied far less, and the assessments say so.
This is a reason to be careful rather than a reason to be alarmed, and it is a reason to treat sunscreen choice on broken or inflamed skin as a question for a pharmacist or a clinician rather than for a website.
If you are choosing a product for skin that is broken, inflamed, recently treated, or affected by a condition such as eczema or a photosensitivity disorder, ask a pharmacist, your GP or your dermatology team. General information about ingredient labelling cannot substitute for advice about your own skin.
In short
Nano in brackets is a fact about particle size that the law requires you to be told. Non nano on the front of a pack is a claim the company chose to make. The first is regulated, defined and verifiable. The second is none of those things, and the safety implication usually attached to it is not supported by the assessment work on dermal use.