It grew something

Mold on the surface, a cloudy patch, a smell that was not there, gas lifting a lid. This is the failure that stops being a business problem and becomes a safety one.

What it looks like

Often nothing, which is the difficulty. Visible mold is the late stage. Bacterial contamination frequently shows as a subtle change in smell, a shift in pH, or a thinning of the product before anything is visible.

By the time a customer can see it, the product has been contaminated for some time and they have been using it.

Where it came from

Three routes, and the third is the one most brands under-weight.

Raw materials. Water, botanical extracts and clays all carry a microbial load. Water in particular is not an inert diluent.

Manufacture. Equipment, containers, hands and air. Every surface the product touches after the phases are combined is a route in.

The customer. The challenge test uses organisms representing household contaminants precisely because a jar in a bathroom is re-inoculated on every use. This is the route a formula has to survive for months without you present.

Why you cannot fix the batch

There is no kill step at the end of skincare manufacture. You cannot pasteurize a finished emulsion without destroying it, and adding preservative to a contaminated batch does not undo the contamination or the metabolites already produced.

A contaminated batch is a disposal, and if it has shipped it is a recall.

What to do

Prevention is the only available strategy, and it is a system: water activity, a preservative active at your pH, a chelator, a package that limits exposure, and manufacturing discipline.

Then evidence: a challenge test on the final formula in the final package, five organisms over twenty-eight days. A brand that has not run one does not know whether its product is preserved. It believes it is.

References