Nanomaterials are not just used in various areas of scientific research, but are increasingly found in consumer products. Particularly the cosmetic and textile industries, as well as the medical branch benefit from the specific chemical and physical properties of nanoparticles (NPs). However, the knowledge base concerning the potential health hazards that nanomaterials hold for humans is far from complete. NPs mainly enter the organism via the lungs or the gastrointestinal tract, where they can accumulate. Transcutaneous penetration is most unlikely in the case of healthy skin. Chronic inflammatory reactions of the airways are particularly relevant in the context of potential risks to human health. Evidence for a geno- and cytotoxic potential of some of the most frequently used NPs is available from cell culture and animal experiments. Therefore, the risk of NP-induced cancerogenesis cannot be ruled out. Currently available nanotoxicological data is partly contradictory, due to differing characteristics of the tested substances and variable experimental settings. Long-term studies using continuous NP exposure in consumer-relevant dosages are needed. Additionally, the molecular mechanisms of NP-induced toxicity have to be elucidated in detail.