White Cast

A white cast is the pale, ashy or greyish film a sunscreen can leave on skin. It is an optical effect: the same particles that scatter ultraviolet light also scatter visible light, and on deeper skin tones the mismatch is far more visible than on light ones.

Mineral filters cause it most often, because zinc oxide and titanium dioxide are white powders that sit on the surface. How obvious it is depends on particle size, how much filter the formula uses, what the filter is dispersed in and how the product is applied. Organic filters, which dissolve rather than sit as powder, usually leave less of one.

• Tinted mineral sunscreens use iron oxides to cancel the whiteness rather than reduce the filter.
• Hybrid formulas cut the mineral load by adding organic filters where they are approved.
• Applying in thin layers and letting each settle before the next reduces the visible film without lowering the amount used.

The one thing not worth doing is using less sunscreen to avoid a cast, since the protection on the label assumes a full application. If every mineral option looks grey on your skin, changing product is the answer rather than changing quantity — and product ranges have improved a great deal on this specific point.