5. Conclusion

Before concluding on titanium dioxide and silver nanoparticles in contact with the skin, it should be remembered that hair follicles are particularly studied in dermatology; they are thought to act as reservoirs for nanoparticles used to treat certain skin diseases. It should also be remembered that quantum dots are capable, under certain conditions, of passing through the epidermis into the dermis, and that zinc from the zinc oxide incorporated in certain sun creams has been measured in the blood and urine of the volunteers who took part in the tests, implying a passage into the bloodstream.

As far as we know, in healthy skin, titanium dioxide and silver nanoparticles penetrate the stratum corneum, the horny layer of the epidermis, and are unable to reach the living layers of the epidermis, with some accumulating in hair follicles. However, one study found titanium...