Anhydrous products, which change the rules

Take the water out and almost every rule in this property changes. Anhydrous products are a genuinely different safety proposition, and they are the easiest place for a new brand to start.

No water, no growth

Microorganisms need available water. An oil, balm or anhydrous cleansing product has essentially none, so there is nothing to support growth and no preservative is required in the sense an emulsion requires one.

Water activity is the concept underneath this. Above roughly 0.75 growth is supported; a true anhydrous product is nowhere near it.

What you still have to worry about

Rancidity. Oxidation of the oil phase is chemical rather than microbial, and an antioxidant addresses it. An anhydrous product that goes off smells of old nuts and crayons, and it is not a safety failure but it is a product failure.

Stability in the physical sense: balms grain, crystallize, or separate if the fats were cooled badly.

Safety substantiation, which applies regardless. No water does not mean no obligation.

Where the water sneaks in

This is the part that catches people. A product designed anhydrous becomes a preservation problem the moment water is introduced, and water is introduced by a wet finger in a jar, by a humectant such as glycerin that draws moisture in, or by an extract supplied in a water or glycol base.

An anhydrous product in a jar, used with wet hands in a bathroom, is not quite the untouchable thing the water activity number suggests. Which is why broad-spectrum protection is sometimes still specified for anhydrous products sold in open jars.

When to choose it

To start. An oil, a balm or an anhydrous cleanser removes the hardest problem in the craft while you learn the rest: sourcing, labeling, packaging, stability, and selling.

It is also a real category rather than a training exercise, and several of the most durable small skincare brands never make an emulsion at all.

References