Colloidal oatmeal

Colloidal oatmeal is oat milled fine enough to stay suspended in water. It is the ingredient in most eczema baths and a great many soothing creams, and it has been used for that purpose long enough that the regulation simply recognises it.

Two things about it are unusual, and they point in opposite directions.

A minimum rather than a maximum

Almost every entry in the skin protectant regulation sets a ceiling. Zinc oxide is permitted at 1 to 25 percent, lanolin at 12.5 to 50 percent, petrolatum at 30 to 100 percent.

Colloidal oatmeal is listed as 0.007 percent minimum, and 0.003 percent minimum when combined with mineral oil.

That is a floor. The regulation is not limiting how much may be used; it is stating how little will do, below which the product may not claim the active.

Since a skin protectant claim makes the product an over-the-counter drug, the proportion appears in the Drug Facts panel, so you can read the figure. That is the same mechanism covered on Petrolatum and it is one of the few places in personal care where a number is printed at all.

It also means the marketing phrase “with colloidal oatmeal” on a product that makes no protectant claim is a different statement entirely. There, the oat is somewhere in the ingredient list in an unstated amount, and the panel that would have told you is absent.

The oat question, which cosmetics cannot answer

Oats do not contain gluten in the sense wheat, barley and rye do. What they very often contain is wheat, picked up in the field, the mill or the transport, which is why oats sold as gluten free are grown and handled under a separate protocol and tested.

On food, that has machinery behind it: a gluten-free claim is a regulated statement with a measured threshold, which is the point the page for people avoiding gluten keeps returning to, and it is why Barley malt extract is a real trap and oats are a manageable one.

On a cosmetic, there is no machinery at all. No gluten declaration is required, no threshold applies, and the INCI name Avena Sativa Kernel Flour tells you the plant and nothing about how it was handled.

What it is actually doing

Not moisturising in the usual sense. It forms a film that holds water against skin and buffers it slightly, which is why it turns up in products for eczema, chickenpox and poison ivy rather than in ordinary face creams.

That also means it is doing the same job as the greasier protectants, by a different mechanism, and the regulation permits several of them to be combined. If your skin does badly with occlusive products, the oat route is the alternative that exists inside the same regulatory category, which is a more useful thing to know than any claim on the front of a box. The page for skin that reacts to everything takes the same approach.