Pesticides are very common in these categories which are used against various pests for human welfare but they are also harmful to us via food chain. Pesticides are used from ancient times in agriculture and in repelling insects from houses. There are many categories of insecticides such as pyrethroids, organochlorine, organophosphate, carbamate and natural compounds. Natural compounds are very costly and not used in general. Pyrethroids are used in house (In all mosquito repellents- coils, mats and liquids) and organophosphates mainly used in agriculture. All these categories affect humans by direct or indirect mechanisms. To assess this damage, lambda cyhalothrin has been selected to observe their effects fishes and the primary effects have been observed on haematology.