Microfine zinc oxide is a superior sunscreen ingredient to microfine titanium dioxide.
BACKGROUND
Microfine zinc oxide and microfine titanium dioxide are particulate sunscreen ingredients that absorb broad-spectrum ultraviolet (UV) irradiation.


OBJECTIVE
We compare microfine zinc oxide and microfine titanium dioxide for their abilities to attenuate UVA radiation and their relative whiteness in cosmetic formulations.


METHODS
UVA attenuation was measured by diffuse reflectance spectroscopy on normal human skin in vivo. Whiteness was determined by reflectance density of dried coatings on a black background of the two particulates at varying concentrations.


RESULTS
Microfine zinc oxide demonstrates superior protection compared to microfine titanium dioxide in the UV spectrum between 340 and 380 nm. Microfine zinc oxide is less white than titanium dioxide at all concentrations.


CONCLUSIONS
Microfine zinc oxide is superior to microfine titanium dioxide as a sunscreen ingredient. It is more protective against long-wave UVA and is less white at a given concentration.
Pinnell
S R
SR
Division of Dermatology, Duke University Medical Center, Durham, North Carolina, USA. pinne002@mc.duke.edu
Fairhurst
D
D
Gillies
R
R
Mitchnick
M A
MA
Kollias
N
N
D006801:Humans; D010316:Particle Size; D012867:Skin / Q000528:radiation effects; D013053:Spectrophotometry; D013473:Sunscreening Agents; D014025:Titanium; D014466:Ultraviolet Rays; D015034:Zinc Oxide
D013473:Sunscreening Agents; C009495:titanium dioxide; D014025:Titanium; D015034:Zinc Oxide