Zinc oxide

What it is

Zinc oxide is a white mineral powder used on skin for centuries. In sunscreen it sits on the surface and absorbs and scatters both UVB and UVA light, which is why it is called a physical or mineral filter¹. In nappy creams it forms a water-repellent layer that protects sore skin from moisture and friction^{4, 5}.

What the evidence says

Evidence: strong. Regulator-approved as a broad-spectrum sunscreen filter and skin protectant, with decades of use and good safety data on intact skin.

The US FDA proposes zinc oxide and titanium dioxide as generally recognised as safe and effective at up to 25%, while asking for more data on most chemical filters². Dermatologists recommend them for sensitive skin and babies, and advise everyone to use broad-spectrum SPF 30 or higher¹. As a skin protectant, zinc oxide at 1 to 25% is an approved over-the-counter ingredient⁵, and dermatologists advise a thick layer of zinc oxide cream for nappy rash, left in place between changes⁴.

On nano versus non-nano: a decade of imaging studies in human volunteers found no penetration of zinc oxide nanoparticles beyond the outer dead layer of skin³. The open question is inhaling loose particles, a reason to prefer creams over sprays and powders. The real trade-off is cosmetic: non-nano zinc leaves a heavier white cast.

For brown and Black skin the white cast is the practical barrier. Tinted mineral sunscreens use iron oxides, which also block visible light, a wavelength that deepens dark spots and causes lasting darkening in deeper skin tones^{1, 6}. See our guides to sun protection for every skin tone and melanin-rich skin care.

How people use it

• Daily sunscreen: broad-spectrum SPF 30 or higher, applied generously 15 minutes before going out and reapplied every two hours or after swimming or sweating¹.
• Tinted or sheer formulas: a tint matching your skin avoids the grey cast on deeper tones; sheer nano formulas are another option.
• Nappy rash or chafing: a thick layer of zinc oxide cream at each change, removed fully once a day⁴.

Cautions

• Apply generously and reapply; a thin layer gives far less than the SPF on the tube.
• Avoid sprays and loose powders near the face, and keep any sunscreen out of the eyes.
• Reactions are usually to fragrance or preservatives rather than the zinc; patch test new products.
• Keep babies under six months in shade and clothing; if impossible, dermatologists prefer a small amount of a mineral product¹.
• Nappy rash with blisters, pus, fever or no improvement after treatment needs a doctor⁴.