Zinc and titanium oxides: promising UV-absorbers but what influence do they have on the intact skin?

Suspensions (20%) of microfine and ACS grade zinc oxide, or 20% titanium oxide in water, castor oil or polyethylene glycol were applied topically to rabbit skin over 4 h (1 day) or 2 h daily (3 days). Skin sites were analysed for metal uptake. Percutaneous absorption of the oxides was probably low, most remaining on the skin surface. Uptake patterns were influenced by the vehicles used. Appreciably more microfine zinc oxide was taken up by the skin in subacute studies. Local changes in trace metal concentration were construed as evidence of percutaneous absorption of zinc and titanium oxides. Further studies are indicated to validate the significance of these preliminary observations.