This review discusses the health risks of nanoparticles, highlighting their potential to enter the human body through the skin, lungs, and intestinal tract. Nanoparticles range from large particles like carbon black to tiny quantum dots. While nanotechnology offers benefits, concerns about their health effects are growing. The review covers the mechanisms by which nanoparticles enter the body, their pathways inside the body, and the experimental results on their bioactivity. It emphasizes the importance of understanding nanoparticle behavior to assess their safety. The skin acts as a barrier, but nanoparticles can penetrate it, especially if they are small. The lungs are a major entry point for inhaled nanoparticles, which can reach the alveoli and cause inflammation. The intestinal tract allows the absorption of macromolecules, with nanoparticles potentially entering the bloodstream. The review also discusses the systemic translocation of inhaled particles, which can affect other organs, including the cardiovascular system. Nanoparticles can interact with biological systems in various ways, including causing oxidative stress, inflammation, and fibrosis. The surface properties of nanoparticles, such as charge and surface area, influence their toxicity and ability to penetrate biological barriers. The review highlights the importance of studying nanoparticle behavior to ensure their safe use in consumer and industrial products. It also notes that the bio-persistence of certain nanoparticles, like asbestos and silica, can lead to long-term health effects. The review concludes that further research is needed to fully understand the health risks of nanoparticles and to develop safe applications of nanotechnology.This review discusses the health risks of nanoparticles, highlighting their potential to enter the human body through the skin, lungs, and intestinal tract. Nanoparticles range from large particles like carbon black to tiny quantum dots. While nanotechnology offers benefits, concerns about their health effects are growing. The review covers the mechanisms by which nanoparticles enter the body, their pathways inside the body, and the experimental results on their bioactivity. It emphasizes the importance of understanding nanoparticle behavior to assess their safety. The skin acts as a barrier, but nanoparticles can penetrate it, especially if they are small. The lungs are a major entry point for inhaled nanoparticles, which can reach the alveoli and cause inflammation. The intestinal tract allows the absorption of macromolecules, with nanoparticles potentially entering the bloodstream. The review also discusses the systemic translocation of inhaled particles, which can affect other organs, including the cardiovascular system. Nanoparticles can interact with biological systems in various ways, including causing oxidative stress, inflammation, and fibrosis. The surface properties of nanoparticles, such as charge and surface area, influence their toxicity and ability to penetrate biological barriers. The review highlights the importance of studying nanoparticle behavior to ensure their safe use in consumer and industrial products. It also notes that the bio-persistence of certain nanoparticles, like asbestos and silica, can lead to long-term health effects. The review concludes that further research is needed to fully understand the health risks of nanoparticles and to develop safe applications of nanotechnology.