A rapidly developing technology, nanotechnology has a significant impact on several therapeutic application domains. Nanotechnology, developed in 1974, focuses on creating materials with a size between 1 and 100 nanometers. It has applications in research, agriculture, and infection treatment delivery tests. Numerous issues pertaining to the welfare and productivity of animals can be resolved by it. Despite their distinctive benefits and uses in both the home and commercial areas, the usage of materials with diameters in nanometers have inspired concerns about worker, consumer, and environmental safety. Nanoparticles have the potential to harm humans and animals through interactions through a variety of processes due to their little dimensions and other distinctive properties. In this review article we have reported and mentioned the toxicity of different selected types of nanoparticles especially metallic nanoparticles such as gold, titanium dioxide, silver, iron oxide and manganese oxide nanoparticles and in addition, we focused on their mechanisms of action of toxicity on central nervous system especially on brain.