Stratum corneum is an effective barrier to TiO2 and ZnO nanoparticle percutaneous absorption.

BACKGROUND: There is increasing concern over the local and systemic side effects of TiO(2) and ZnO coated nanoparticles widely used in sun blockers. OBJECTIVE: To determine the localization and possible skin penetration of TiO(2) and ZnO nanoparticles, dispersed in 3 sunscreen formulations, under realistic in vivo conditions in normal and altered skin. METHODS: Nuclear microscopy techniques provided spatially resolved quantitative analysis of Ti and Zn nanoparticle distributions in transversal cryosections of skin obtained by biopsy with no further treatment. A test hydrophobic formulation containing coated 20-nm TiO(2) nanoparticles and 2 commercial sunscreen formulations containing TiO(2) alone or in combination with ZnO were tried, taking into account realistic use conditions by consumers and compared with the recommended standard condition for the sun protection factor test. The protocols consisted of an open test. RESULTS: Following a 2-hour exposure period of normal human skin to TiO(2)- and ZnO-containing sunscreens, detectable amounts of these physical blockers were only present at the skin surface and in the uppermost stratum corneum regions. Layers deeper than the stratum corneum were devoid of TiO(2) or exogenous ZnO, even after 48 h of exposure to the sunscreen, under occlusion. Deposition of TiO(2) and ZnO nanoparticles in the openings of the pilosebaceous follicles was also observed, suggesting a preferential fixation area. Penetration of nanoparticles into viable skin tissue could not be detected. CONCLUSIONS: TiO(2) or ZnO nanoparticles are absent or their levels are too low to be tested under the stratum corneum in human viable epidermal layers. Therefore, significant penetration towards the underlying keratinocytes is unlikely.

Cryosurgical treatment of a large keloid.

The cryosurgical treatment of a patient with a large keloid on the nuchal region is reported. The tumor was frozen under local anesthesia with minimal discomfort. The temperatures beneath the lesion were monitored in order to achieve a deep freezing. Twelve months after the treatment the tumor has not recurred.

Musk ambrette and chronic actinic dermatitis.

A patient with persistent photosensitivity and positive photopatch tests to musk ambrette and an after-shave lotion is reported. Phototests showed extreme sensitivity to UV radiation, especially UVB. Patch tests with the European Standard Series and some plant allergens were negative. Histology showed a granulomatous reaction with epithelioid and giant cells in the dermis.