The amount of reactive oxygen species increased in cells of hosts infected with parasites as reported by a number of studies. The excess of free radicals in the parasitised cells depends on the nutritional status of the host, the degree of parasitic infestations and on the destructive effect on tissue, and reported associating blood parasites like Theileriosis, Babesiosis and Trypanosomosis. In addition, external parasites and endoparasites such as Fasciola sp., Trichostrongylus sp. and Eimeria sp. had been reported to be associated with lipid peroxidation. The current review throws light on parasitic infestations associated with oxidative stress and their harmful effect.