What does a nano spray sunscreen need before it can be notified?

The inhalation route is the whole question, and it has to be settled before the formula is developed, not before launch.

A spray creates an inhalable aerosol. Nano TiO2 or ZnO reaching the lung is a different risk assessment from the same material on skin, and several markets restrict or add requirements for sprays containing nanomaterials. Check the target market first: if the answer is no, no amount of formulation work helps.

Technically, a spray needs low viscosity and clean atomisation, which means the dispersion must stay stable over the shelf life — otherwise the actuator clogs and the dose per actuation drifts. Powder settling in the can is the other failure mode.

Test spray pattern, dose per actuation and the particle-size distribution of the aerosol, not just formula stability. A product that delivers 0.6 mg/cm² per pass will not be used at the labelled rate whatever the bottle says.

Where the regulatory position is tight, the workable route is to position the product as a sprayable lotion that still needs rubbing in, and to put clear usage directions on the pack — do not spray directly at the face.